Continuation Study to Evaluation the Impacts of the SR 91 Value-Priced Express Lanes
Final Report

 

Printable Version (PDF 2.38MB)

CONTENTS:

• Executive Summary
• 1. Introduction
  • 2. Traffic, Trends, Driving Conditions, and Transit
  • 3. Investigation of Corridor Travel Behavior
  • 4. Assessing Public Opinion
  • 5. Modeling of Travel Choice and Elasticities
  • 6. Collision Trends and Characteristics
• 7. Analysis of Emissions
• 8. Conclusion
• End Notes

  

Executive Summary

This is the follow-up final report for a Caltrans and U.S. DOT-sponsored study to identify the impacts of the value-priced express lanes which opened on December 27, 1995 in the median of State Route 91 in Orange County, Ca. As the first practical application of value pricing in the United States, this project provides many important insights, both technical and institutional. Some of these insights pertain to implementing value-pricing projects in other locations.

This report documents more than five years of field observations, including about a year and a half of observations to establish baseline conditions before the facility opened. Data collection included traffic measurements, vehicle occupancy counts, transit ridership data, and comprehensive travel surveys with current and former commuters. Data analysis included calibration of models of the route (toll/non-toll), vehicle occupancy, transponder acquisition, and time-of-day choices of commuters; as well as estimation of air pollution emissions. The current report contains findings through mid-1999, supplementing a previous "final report" issued May 1998, which presents impacts through June 1997.¹

The study also produced an extensive data set which is itself an important study product, since it provides opportunities for other researchers to explore aspects of the express lanes which are beyond the scope of the current study. Key elements of the data set are available on-line at http://ceenve.calpoly.edu/sullivan/sr91/sr91.htm

The section of California State Route 91 (SR 91) containing the express lanes is located between the SR 91/SR 55 junction in Anaheim and the Orange/Riverside County Line. The project provides two extra lanes in each direction, separated from the adjacent freeway by a "soft" barrier consisting of a painted buffer with pylons. The SR 91 Express Lanes, which we refer to as the "91X lanes," incorporate a number of innovative features. These include tolls which vary throughout the day in relation to demand and to congestion on the parallel freeway, the requirement for users to be registered customers and carry transponders, the use of discounted tolls as an incentive to high occupancy (3+) groups, photo-enforcement of toll violations, and the development and operation of the facility as a for-profit private enterprise.

Summary of Principal Findings

Continuing experience shows that increasing numbers of commuters are willing to pay tolls to enjoy the benefits of reduced travel time, improved driving comfort, and the perception of improved safety. Although the majority of commuters do not find it worthwhile to pay the tolls every commute trip, with time and increasing congestion the percentage of toll lane users has increased. While the frequency of toll lane use varies significantly with income, gender, age, and other characteristics, people from all demographic backgrounds use the facility. Our analysis shows that being female is the factor most strongly associated with toll lane use, while high income, age, education, and traveling to work all influence travelers' likelihood of obtaining transponders.

The express lanes are located in what had been one of the most heavily congested freeway corridors of California, with typical peak period delays before the project of 30-45 minutes.

During the height of the peak, the 91X lanes now accommodate 1400-1600 vehicles per hour per lane, about the same as the adjacent freeway and more than the freeway had previously accommodated when severely congested before the 91X lanes opened. The presence of the value-priced by-pass lanes has resulted in an equilibrium under which the overall facility operates better than before. As a further benefit, commuters have the option to travel congestion-free on occasions when the value to them of doing so exceeds the toll.

Although the impacts of the 91X lanes on corridor traffic conditions have been largely favorable, freeway congestion has continued to increased, and the recent opening of the Eastern Toll Road (ETR)² has worsened that congestion, especially in the eastbound direction where eight lanes of traffic must now merge into six lanes where the SR 91 crosses the county line. Increased congestion has been accompanied by increased toll facility use (91X and ETR combined) and a decline in the proportion of non-work trip purposes during peak periods.

The opening of the 91X lanes in 1995 and of the ETR in 1998 were both accompanied by significant jumps in peak period traffic, in which the single occupant vehicle (SOV) component was the largest part. This resulted in an initial decrease in corridor average vehicle occupancy (AVO), which has remained stable subsequently. In addition, the opening of the 91X lanes in 1995 was accompanied by a one-time 40% increase in the corridor of vehicles with three or more occupants (HOV3+), probably related to the policy, for the first two years of operation, of allowing HOV3+ traffic to use the 91X lanes for free. The beginning, in early 1998, of charging HOV3+ users 50% of the published toll, did not change the overall level of HOV traffic in the corridor, however HOVs do not use the 91X lanes as frequently as before. In all, concerns that the value-priced facility might cause erosion in ridesharing as well as in public transit use in the corridor have not materialized.

Value pricing is associated with highly selective travel behavior. Although the proportion of commuters who use the lanes has increased, among those who use the facility, the proportion who use it for half or more of their peak trips has decreased. The "91 Express Club," which provides toll savings for persons making more than 20 toll lane trips per month, attracts only a small portion (about 12%) of transponder-holders.

The traveler's decision to use the toll lanes is very closely related to hour-by-hour variations in traffic conditions. Our analysis shows that peak period commuters on SR 91 value time at approximately $13-16 per hour, and that demand is moderately price-sensitive, which demonstrates substantial scope for fine-tuning hourly demand through time-variable tolls.

New toll schedules first implemented in September 1997 introduce hour-by-hour toll differences in peak periods. As yet, the fairly small differences in the hour-by-hour tolls have not been accompanied by much flattening of the peak period traffic distributions.

Travelers who choose to pay tolls consistently overestimate their time savings. In addition, drivers cite easier driving and perceived safety as the two main reasons for using the toll lanes besides perceived time savings. The number of toll lane users who say the 91X lanes are safer than the freeway lanes outnumber those who say the express lanes are less safe by a 4:1 margin.

Accident rates for the Orange County section of SR 91 containing the toll lanes decreased significantly after the toll lanes opened, an effect which may be due to decreased congestion or the conclusion of construction activities. At the same time, accident rates increased in the Riverside County section of SR 91 just east of the toll lanes. There is visual evidence of rates increasing in both sections since 1996, but statistical tests are inconclusive. Overall, estimated accident rates in the Orange County section containing the 91X lanes compare favorably to the other road sections investigated.

An aggregate modeling analysis indicates that corridor emissions with the 91X project are about the same as would have occurred if dual HOV lanes or dual general use lanes had been constructed instead.

Although financial performance was not directly investigated in this study, corporate reports indicate that a value-priced facility can be financially successful in a carefully selected market. Even given the direct competition and congestion problems which followed the opening of the new Eastern Toll Road (ETR), the 91X project is reportedly maintaining acceptable financial performance, and the project appears poised to yield a favorable rate of return through its lifetime. On the other hand, it is rare for an urban highway project to enjoy the 91X's unusual combination of modest capital requirements (less than $3.5 million per lane-mile), large demand, and a favorable institutional environment for quick implementation.

Recent, highly public controversies have surrounded the use of the "non-compete" provision in the project franchise agreement to limit nearby corridor improvements by Caltrans, as well as CPTC's attempt to sell the project to a separate non-profit corporation. It appears likely that a recent significant decrease in commuters' approval of variable tolls reflects these controversies. Nevertheless, our survey respondents remain generally positive about using innovative pricing to expand travel opportunities through high occupancy toll (HOT) lanes. Because of the influence of the recent controversies, the jury is still out regarding the public's acceptance of public-private partnerships for accelerating development of needed highway capacity.

List of Specific Findings

The following is a full list of our principal study findings concerning impacts on traffic, changes in travel behavior, and public opinions. The data and analyses which support these findings appear in the body of the report. Cross references are provided showing where in the text can be found detailed information supporting each finding.

The list of findings are grouped by topics which generally follow the order in which the material appears in the body of the report.³

Overall Traffic Trends and Toll/Non-Toll Facility Shares

• The 91X lanes carry a substantial share of the weekday traffic in the SR 91 corridor. After opening day, weekday 91X lane traffic increased steadily until the opening of the Eastern Toll Road (ETR) in October 1998. By September 1998, the total weekday two-way average daily traffic (ADT) using the 91X lanes had reached its peak level at about 33,000 vehicles per day (over 14% of the total weekday SR 91 ADT). Weekday 91X traffic then decreased steadily during the first 6-8 months after the ETR opened. By summer of 1999, the 91X weekday traffic had reached about 24,000 vehicles per day, with no further decreasing trend evident. (Section 2.3, Figure 2-1.)
• 91X traffic in the morning peak direction has been consistently less than in the afternoon peak direction, when congestion in the free lanes is worse. After the ETR opened, that difference increased. 91X lane traffic as well as ETR traffic on Friday afternoons consistently and significantly exceeds all other periods. (Figure 2-3 and Figure 2-4.)
• The trends in 91X weekend traffic have been different from weekdays. The highest weekend ADT values were about 20,000 for a Saturday, reached in August 1998, and about 17,500 for a Sunday, in May 1997. The effect of opening the ETR on weekend 91X traffic was not as great as for weekdays. (Figure 2-2.)
• The weekday ADT on SR 91 (free and toll lanes combined) increased substantially during the months following the capacity increase from opening the toll lanes. The average midweek ADT increased by about 32,600 daily trips between the last quarters of 1995 and 1996, nearly a 17% jump in total daily traffic. Over the same period, midweek 91X lane traffic grew to 24,500 vehicles per day. Between the last quarter of 1996 and the third quarter of 1998, just before the ETR opened, the SR 91 total midweek ADT (free plus toll) increased another 3,650 trips (1.6%), while the 91X ADT increased by 6,900 trips to about 31,400. By September 1998, the 91X lanes carried over 85% of the cumulative growth in corridor traffic (31,400 of 36,300) since the toll lanes opened in December 1995. (Section 2.6, Figure 2-22 and Figure 2-23.)
• During its first three months of operation (October-December, 1998), the average midweek ADT on the new ETR toll highway reached 21,200 vehicles per day. This occurred at the same time as the 91X toll lane traffic decreased 3,900 vehicles per day, and the SR 91 free lane traffic decreased 7,400 vehicles per day. The remaining 9,900 vehicles per day is the estimated increase in overall corridor traffic (ETR plus SR 91 -- free and toll, measured at the 91X midpoint). Because the ETR serves some trips between locations entirely within Orange County, only part of this increased traffic crosses the county line. Also, a small portion of the increase may be double-counted. (Figure 2-24.)
• Rough estimates available from ramp counts suggest that just over 20% of the total SR 91 traffic increase (free plus toll) in the first year after the 91X lanes opened (about 7,000 of 32,600 vehicles per day) may be traffic returning to the state highway from parallel city streets. Although traffic congestion on SR 91 increased between 1996 and 1999, the shift of traffic back to the freeway from parallel arterials which accompanied the opening of the 91X toll lanes has mostly continued. (Section 2.7, Figure 2-26.)
• During its second and third quarters of operation, the midweek ADT on the new ETR increased steadily, reaching an average of 33,100 vehicles per day in May-July, 1999. The growth in ETR traffic during this seven month period (+11,900 vehicles per day) was accompanied by a further 5,900 vehicles per day decrease in traffic on the 91X toll lanes. In all, the total decline in 91X traffic by summer 1999 corresponds to about 30% of the total ETR traffic growth during the same period. (Section 2.6, Figure 2-1 and Figure 2-7.)
• Throughout the study period, traffic volumes remained stable in the SR 57/60 freeway corridor located roughly parallel to SR 91, about 16 km. (10 mi.) to the north. In addition, field observations showed no association between opening the 91X toll lanes and changes in HOV traffic using the SR 57/60 corridor. This indicates that the influence of the toll lanes, while locally important, did not induce detectable traveler route shifts at the regional scale. (Section 2.7, Figure 2-25.)
• CPTC reported it had issued about 124,000 transponders by the end of 1999, joining approximately 240,000 transponders issued by the public toll road authority (the TCA) in Orange County. (Section 2.3.)
  
  Adjustments Accompanying Changes in Tolls and Traffic Conditions
• The first general toll increases which occurred in January 1997 was followed by a significant and permanent reduction in the rate of 91X traffic growth. Subsequent general toll increases, which were less substantial and focused on fine tuning of the hour-by-hour toll schedule, were not followed by visible changes in the overall 91X ADT trend. (Section 2.3, Figure 2-1.)
• There exists a strong correlation between express lane patronage and time of day dependent travel time savings. Over the entire period of observation, the percentage of SR 91 travelers who used the express lanes ranges from about 7% in the midday off-peak, when time savings are minimal, to around 35% in the heaviest PM peak hour when delays to freeway users are worst. The implied values of time for persons who use the toll lanes during the peak hour range from $6 to nearly $14.⁴ Since our surveys with peak period travelers show that 91X commuters consistently overestimate their actual time savings when paying tolls, the actual values of time are lower than these estimates. (Section 2.9, Figure 2-35 through Figure 2-37.)
• The increased capacity from adding two new toll lanes in each direction in December 1995 substantially reduced peak period congestion in the entire Orange County SR 91 corridor, giving short-term travel time benefits to all commuters. In the six months after the express lanes opened, the typical PM peak trip delay on the freeway fell from 30-45 minutes to 510 minutes per trip. Subsequently, delays increased gradually to October 1998 when they jumped to the 30-40 minute range following the opening of the ETR. During the first half of 1999, delays decreased somewhat, to about 30 minutes in the PM peak and less in the AM peak. (Figure 2-31.)
• Time of day distributions of SR 91 traffic show that, in 1996, soon after the express lanes opened and the increased highway capacity no longer constrained demand, the PM peak traffic distribution changed to become much sharper than prior to and shortly after the opening. The reemergence of a sharp afternoon peak at approximately 5:00 PM occurred in the presence of a toll schedule which charged the same amount, $2.75, for the entire period from 3:00 to 7:00 PM. The introduction of a more differentiated toll structure in September 1997, with tolls varying by the hour, had little effect on the sharpness of the overall afternoon time of day distribution for the corridor, or of the 91X traffic specifically. However, in the morning peak, there did occur a small amount of peak flattening accompanying the more substantial hourly toll differences which were implemented during that time. (Section 2.8, Figure 2-27 and Figure 2-28.)
  
  Observations about Ridesharing and Transit
• 14. Within three months after the SR 91 toll lanes opened, PM peak traffic observations on all lanes of the highway showed a greater than 40% jump in high occupancy vehicles carrying three or more people (HOV3+). At that time, HOV3+ vehicles paid no toll, although they were required to have transponders. (Section 2.10, Figure 2-38.)
• When HOV3+ users were charged a 50% toll in January 1998, about a third of the HOV3+ traffic (about 2,000 vehicles per day) left the 91X lanes, and HOV3+ traffic in the free lanes increased by the same amount. These changes occurred mostly during the shoulder hours and throughout the week, although much less on Friday afternoon. Following these changes, the total PM peak HOV3+ traffic in the corridor remained the same. (Figure 2-17 and Figure 2-38.)
• Through the entire period of observation, from 1994 through 1999, the counts of PM peak dual occupant (HOV2) vehicles remained essentially unchanged. HOV2 users of the express lanes pay the same tolls as SOV users, or half the toll on a per person basis. (Section 2.10, Figure 2-39.)
• The increase in HOV traffic which occurred after the toll lanes opened is measured relative to a small initial base. For example, throughout 1995, before the express lanes opened, HOV3+ vehicles averaged about 4% of the total SR 91 PM peak traffic. After the express lanes opened, the comparatively much larger growth in single occupant vehicle (SOV) traffic produced a small but statistically significant decrease in average vehicle occupancy (AVO). The AVO trend leveled off during the past few years. Notwithstanding the initial reduction in AVO, the counts of HOV2 and HOV3+ commuters increased significantly compared to the conditions which existed previously. (Section 2.10, Figure 2-44.)
• There is no evidence that the opening of the 91X lanes or the ETR impacted the development of public transportation patronage in the corridor, particularly the IEOC commuter rail line. The rail service has competed successfully throughout the observation period for a small share (<1%) of the commute market. (Sections 2.11 and 2.12, Figure 2-45 and Figure 2-46.)
  
  Findings Concerning the Amount of Trip Making and Trip Purpose
  
  
• SR 91 commuters are now using the 91X lanes more than reported after the first year of operation. The proportion of commuters who use the 91X lanes at least some of the time increased from 28.2% in 1996 to 42.0% in 1999. (Section 3.4, Table 3-I.)
• Worsening congestion has motivated some persons to reduce their peak period travel in the corridor. Of 1057 survey subjects, 224 (21%) no longer regularly travel in the SR 91 corridor in peak periods, but did so within the past two years, and have not changed jobs or home location. Of these, 47% said that changing travel conditions influenced their decisions to stop using the corridor. When asked to explain, 86% cited worse traffic, 18% cited driving stress, and 9% cited higher tolls. Females and commuters in the lowest income group were significantly more likely than other groups to have discontinued commuting in the corridor. (Section 3.13.)
• Changes in the peak period trip purpose breakdown indicate that increasing congestion has pushed some discretionary trips out of the peak periods. In 1996, we observed an increase in peak period non-work travel apparently induced by improved travel conditions shortly following the increase in capacity from opening the 91X lanes. In 1999, these non-work trips had decreased, especially in the PM peak. (Section 3.7, Figure 3-28.)
  
  Findings Related to Ridesharing and Employer Trip Reduction Programs
  
  
• Our previous 1995 and 1996 surveys found that more SR 91 commuters shifted from single occupant vehicles (SOV) to high occupancy vehicles (HOV) than vice versa in the first year after the express lanes opened. Our 1999 surveys indicate that there has been no significant mode shifts since that time. (Section 3.3.)
• HOV commuters are more likely than SOV commuters to choose the 91X lanes. This suggests that the opportunity to split the toll among multiple occupants is a factor in route choice. (Section 3.3, Figure 3-2.)
• 6% of HOV3+ and 26% of HOV2 commuters indicate that they share commuting costs. 34% of HOV3+ groups cite cost-sharing as their principal motivation for ridesharing. Only 19% of the HOV3+ sample rideshare with members of the same household. (Section 3.10, Figure 3-47.)
• Despite the 50% toll discount for HOV3+ commuters on the 91X lanes, the difference in the proportions of HOV2 and HOV3+ groups using the 91 toll lanes is not statistically significant. (Figure 3-2.)
• Work schedule flexibility was found to be unrelated to the level of 91X lane use. This is surprising, since it was expected that schedule flexibility would result in time-of-day shifts to avoid congestion and high tolls. (Section 3.11.)
• The presence of employer rideshare and transit incentive programs was found to be associated with more frequent toll lane use, probably due to those companies having more HOV commuters, who use the toll lanes more than SOV commuters. The ability to telecommute was found to be related to decreased use of toll facilities. (Section 3.11, Figure 3-48 and Figure 3-49.)
  
  Findings Concerning Travel Times and Perceived Travel Conditions
  
  
• Among toll lane users, the magnitudes of perceived time savings increased between 1996 and 1999. As expected, the perceived PM peak savings exceed the AM peak savings. Although travelers appear to accurately perceive the relative magnitude of their time savings, they typically overestimate their actual absolute time savings, by amounts between 5 and 30 minutes. Not surprisingly, both the likelihood of using the 91X lanes and the frequency of use are related to the perceived travel time savings. (Section 3.9, Figure 3-35 through Figure 3-42.)
• Despite the correlation between travel time savings and the percentage of SR 91 traffic using the toll lanes, some toll lane users choose to use the toll lanes under traffic conditions where the expected value of their time savings is clearly less than the tolls paid. In both 1996 and 1999, driving comfort and the perception of greater safety were identified by travelers as the principal motivations for this behavior. Reliability of travel time was cited a distant third. Also noteworthy is that over 15% of transponder holders do not personally pay for their use. The number of toll lane users who say the 91X lanes are safer than the regular freeway lanes outnumber by 4:1 those who say the express lanes are less safe. (Section 3.10, Figure 3-43 and Figure 3-44.)
  
  Findings about Transponder Acquisition and Use
  
  
• About 10% of transponders in our sample are funded by the travelers' employers. Another 5% are funded by a friend, family member, or someone else, and 3% are paid for by a combination of sources. (Section 3.12.)
• Just 12% of the 618 survey respondents who have CPTC transponders report that they belong to the Express Club, which provides a toll savings for those who use the 91X lanes more than 20 times per month. So while commuters are using the 91X lanes more frequently, few commuters are everyday users. (Section 3.12.)
  
  Findings Related to Income and Other Demographics
  
  
• Little has changed since 1996 in the association between income and use of toll facilities. In both 1996 and 1999, the proportions of commuters who chose the 91X lanes increased with income for all modes. The differences are statistically significant among income groups in whether toll or free routes are chosen. One notable change from 1996 to 1999 is the significant decrease in the percentage of trips on toll facilities for the $40-60K income category, from 40% in 1996 to 25% in 1999. This suggests that middle income commuters have been particularly sensitive to the toll increases, and are less willing to pay tolls despite worsening congestion. (Section 3.4, Figure 3-6, Figure 3-8 through Figure 3-13.)
• In general, the proportion of commuters who chose the 91X lanes over the free lanes is higher for females than for males. Only in the HOV3+ category is the proportion higher for males than females. The same trends are apparent when analyzing how frequently commuters report using the 91X lanes (e.g., more females than males are frequent users, except among HOV3+ commuters) and this has been stable over time. However, the only statistically significant differences between the genders are among SOV commuters. (Section 3.5, Figure 3-14 through Figure 3-17.)
• Age is associated with frequency of toll lane use. The youngest and oldest travelers are less likely to be frequent toll lane users than travelers in intermediate age categories. Education level is also directly related to the level of use of the toll facilities. Household type, that is, whether there are children in the home, was found not to be related to the level of toll facility use. (Section 3.6, Figure 3-24 and Figure 3-27.)
  
  Findings about Public Opinion
  
  
• Commuters in the SR 91 corridor draw a sharp distinction in their opinions about toll facilities generally and about the special characteristics of the 91X lanes. Approval for providing toll facilities in general remains high for most commute groups, in the 50-75% range, similar to three years ago. However, approval of variable tolls, which has consistently lagged approval of toll financing in general, decreased significantly from its high point of 55-75% in 1996 to the 30-50% range in 1999. (Section 4.3, Figure 4-1 and Figure 4-3.)
• Current approval of variable tolls varies significantly among groups depending on their method of travel. Among SOV commuters, a very large difference in approval (53% v. 28%) was observed between recent toll lane users and non-users, however no similar difference was observed for HOV commuters. (Figure 4-1 and Figure 4-3.)
• Levels of approval of variable tolls are not very sensitive to commuters' income. Commuters with household incomes above $100,000 were found to show higher approval of variable tolls, as well as of toll financing in general, compared to all other groups. However, no significant differences were found among the different groups with incomes below $100,000. (Figure 4-4.)
• Approval of private companies operating toll roads for profit decreased significantly among all commuter groups between 1996 and 1999, currently showing approval levels in the 3045% range, compared to 50-75% approval in 1996. As noted below, it is evident that public opinions about variable tolls and for-profit operations have been negatively affected by the highly public controversies which recently have occurred in connection with the 91X project. (Section 4.4, Figure 4-5.)
• Corridor commuters express generally high levels of approval (in the 45-75% range) for the idea of selling excess HOV lane capacity to SOV users, provided that this doesn't cause the HOV lanes to become congested. Apparently, the recent public relations difficulties of the 91X project do not extend to other related innovations. (Section 4.4, Figure 4-7 and Figure 4-8.)
• Recent media coverage of the 91X project and CPTC has contributed to negative public perceptions of the project. Well documented problems include worsening congestion and traffic spill-over to residential areas, collisions experience, and charges of irregularity in CPTC's efforts to sell the business to a non-profit organization. Litigation and threatened litigation as well as government investigations have further affected the atmosphere. (Section 4.5.)
  
  Findings about Choice Modeling and Elasticity
  
  
• This part of the work culminated in the development of three final choice model specifications: one joint logit model which only considers choice among the three alternative routes through the corridor (toll and non-toll); and two nested logit models, one which considers choice of mode, transponder acquisition, and route, and another which considers choice of time of day, transponder acquisition, and route. The models relate choices to the travel time and per capita toll for each option, along with numerous trip and traveler characteristics such as gender, age, income, education level, and employer policies on commuting. The models are powerful predictors of toll lane use with good statistical properties and consistency with other study findings. (Table 5-IV, Table 5-VI, and Table 5-VII.)
• The calibrated choice models are robust with plausible parameter values. Model parameters are stable across different specifications, providing predictions, elasticities, and value of time estimates which do not vary much among the various models. (Section 5.9.)
• Certain traveler or trip characteristics increase the willingness of commuters to use a toll road. One of the strongest is being female. Other factors -- high income, middle age, higher education, and being a commuter to work -- appear to affect toll road use more indirectly, by favoring a willingness to acquire an electronic transponder. The combined effect is that women aged 30-50 are more likely to choose a toll road than any other age/gender classification, and this effect seems to hold across different amounts of time savings and toll levels. (Section 5.9.)
• Estimates of travelers' implied average values of time are similar among the preferred models, approximately $13-16 per hour. (Table 5-IV, Table 5-VI, and Table 5-VII.)
• The price elasticity for use of the 91X lanes during the 6-hour period of heaviest use (morning westbound or afternoon eastbound) is consistently about 0.7 to 0.8, based on response to uniform percentage toll changes. This means that a 10% across-the-board toll increase would result in about a 7-8% decrease in toll facility use. More targeted toll increases -- during just the one-hour "peak of the peak" -- yield price elasticities between 0.9 and 1.0. These results demonstrate that there is scope for adjusting toll schedules, even in as small as one-hour increments, in order to regulate traffic levels. (Sections 5.5 and 5.8.)
  
  Findings about Collision Experience
  
  
• For the Orange County section of SR 91 containing the 91X lanes, data show a reduction in fatal and injury (F&I) and total accident rates immediately after opening of the toll lanes. However, it should be noted that the observation period prior to the opening includes the time when the 91X lanes were being constructed. This condition is not usually considered in traffic safety analysis due to the typically unrepresentative traffic behavior patterns during construction. (Section 6.3, Figure 6-1 and Figure 6-2.)
• By late 1997, visual evidence suggests that accident rates on the Orange County SR 91 section had returned to near their 1995 levels, although only an increase in the weekday average F&I rate tests significant. These changes are consistent with past studies which have shown that higher accident rates usually follow increased levels of congestion. (Figure 6-1 and Figure 6-2.)
• For a two-mile section of the SR 91 freeway in Riverside County, between the terminus of the 91X lanes and SR 71, the total accident rate increased for weekdays and for peak periods in the peak direction following the opening of the 91X lanes. The F&I rate for the peak period in the peak direction also increased, but the overall weekday F&I rate did not. These changes are probably due to increased congestion in this section. Recent (1998) increases in the concentration of collisions just west of Green River Road warrant additional detailed consideration. (Figure 6-3 through Figure 6-6.)
• A longer 7.5-mile section of SR 91 in Riverside County, between the Orange County line and Interstate 15, shows a significant upward trend in total peak period, peak direction collisions throughout our entire period of observation. However, no corresponding trend exists for F&I collisions in this section. (Figure 6-8.)
• The overall pattern of accident rate changes on SR 57 for the peak period, peak direction shows no clear changes. This suggests that the peak period differences observed on SR 91 do not reflect a region wide trend. (Figure 6-9.)
• During our observation period, there were generally no systematic changes in peak period collision types in the Orange County section of SR 91 containing the 91X lanes. (Section 6.4, Figure 6-11.)
• After the 91X lanes opened, the percentages of peak period rear end collisions and vehicles reporting slowing/stopping movements increased significantly in the 2-mile section in Riverside County between the county line and SR 71. This suggests the influence of increased congestion in this section. (Figure 6-12 and Figure 6-15.)
• Overall, the available evidence suggests that the 91X facility is operating at an acceptable level of safety.
  
  Findings about Vehicle Emissions
  
  
• If dual HOV lanes had been constructed instead of the 91X toll lanes, and assuming no change in vehicle-miles of travel (VMT), the overall modeled emissions for March 1998 conditions would be approximately the same as with the existing 91X facility. (Section 7.4, Table 7-V.
• If general use lanes had been constructed instead of the 91X toll lanes, the modeled emissions for March 1998 would be approximately the same, assuming that induced traffic produced a 7% traffic (VMT) increase. For other assumptions on increased VMT, ranging from 0% to 10%, overall modeled emissions would vary from 6% less to 3.7% more than the values estimated for the existing 91X facility. (Section 7.5, Table 7-X through Table 7-XIII.)
• If no additional capacity had been built, our best estimate is that VMT would be about 8% less and overall modeled emissions in March 1998 would be 18% less than the values for the existing 91X facility. This analysis is based on very limited data. (Section 7.6, Table 7-XV.)

Closure

The State Route 91 Express Lanes project remains unique in its particular combination of operational and institutional characteristics. The project is poised to undergo additional changes in years to come, in terms of project ownership and organization, in the nature of the competitive relationship with public highways, and in the project's interfaces with new transportation investments in the vicinity. How these changes play out will continue to provide useful lessons for innovative transportation projects in other settings.

Back to Table of Contents

1. Introduction

1.1 Overview

This is the follow-up final report for a Caltrans and U.S. DOT-sponsored study to identify the impacts of the State Route 91 Express Lanes, the nation's first value-priced roadway, which opened on December 27, 1995 in Orange County, California. The express lanes extend about ten miles in the former median of the Riverside Freeway, connecting the major employment centers of Orange County and southern L.A. County with the predominantly residential communities of Riverside and San Bernardino Counties. Tolls in the express lanes vary hour by hour to control demand and maintain free flow traffic, in contrast to often congested traffic conditions in the adjacent free lanes.

The State Route 91 (SR 91) Impact Study began in 1994 under an original contract which provided for studying the corridor's operations through June 1997. At the end of this period, a final report was published in May 1998.⁵ At approximately the same time, several major developments occurred in the operation of the 91 Express (91X) Lanes, which the sponsoring agencies viewed as having potentially important consequences for the use and impacts of the facility.⁶ These include:

• A change to the toll schedule in September, 1997, which for the first time charged different tolls hour-by-hour within the peak period. Previously, the same toll was charged throughout each four-hour peak (and the six-hour PM peak on Friday).
• The beginning in January, 1998, of charging tolls to high occupancy vehicles with three or more occupants (HOV3+), at 50% the published toll. Previously, HOV3+ travelers could use the 91X for free.
• The opening in October 1998 of the Eastern Toll Road (ETR), a fixed-toll highway operated by the Orange County Transportation Corridor Agencies (TCA), which directly competes with the 91X lanes for commute travel to Irvine and vicinity.
• The announced intent of the California Private Transportation Company (CPTC), the private developer and operator of the 91X lanes, to sell the business to a non-profit entity.

Our follow-up study began in March, 1999. Its purpose is to measure and document the impacts of these new developments and to address certain other issues not included in the original study. It extends the period of observation from June, 1997, to late 1999, and extends the scope of the original study to model corridor travel demand and model corridor air quality.

This report presents the complete results of this follow-up work. It supplements but does not replace the May, 1998, report of the original study.

As the first practical application of value pricing in the United States, the 91X project provides a number of important insights, both technical and institutional in nature. Some of these insights are applicable to implementing projects of this nature in other locations.

Most findings in this report and in the previous May, 1998, report are based on the extensive data set developed during the study. These data are an important study product, since they provide an opportunity for others to conduct further investigations of the 91X lanes which are beyond the scope of the current study. The principal data developed by the study are available on-line at: http://ceenve.calpoly.edu/sullivan/sr91/sr91.htm

The following sections provide a detailed description of the 91X lanes and their operation, a synopsis of the major conclusions from the May, 1998, report, an overview of the follow-up study scope and methodology, and a guide to the organization of the rest of this report. Each technical chapter begins with a list of the principal findings contained in that chapter. The concluding chapter is a review of the most important findings and issues raised by the study.

1.2 Description of the SR 91 Express Lanes

The California SR 91 Express Lanes are located in the freeway median between the SR 91/55 junction in Anaheim and the Orange/Riverside County Line. (See Exhibit 1-A and Exhibit 1-B.) The 91X facility provides two extra lanes in each direction, separated from the adjacent freeway lanes by a "soft" barrier consisting of a painted buffer with pylons. (See Exhibit 1-C.⁷) The lanes operate as an express facility; that is, there are no intermediate exits or entrances along the 10-mile length. Heavy vehicles are prohibited from the toll lanes.

The 91X lanes incorporate a number of innovative features which make it one of the most interesting experiments in highway transportation in quite some time.

The toll lanes are located in what had been one of the most heavily congested freeway corridors of California. Before the 91X lanes opened, peak period delays of 20-40 minutes were typical. The capacity increase from adding two new lanes in each direction initially reduced delays in the free lanes to less than 10 minutes. More severe congestion has since returned, although delays are not yet at the level experienced before the 91X lanes opened.

The four-lane, 10-mile long toll facility was constructed for approximately $134 million as a private for-profit investment, one of four such private-public partnership experiments authorized by the California Legislature under the AB 680 legislation enacted in 1989. To date, it is the only AB 680 project operating. One other such project, SR 125 in San Diego County, is under construction and scheduled to open in 2003.

The SR 91 project became a candidate for implementation under AB 680 because of the region's inability to fund necessary improvements in the corridor within a short time frame. Had public funds been used for improvements, the added capacity would have included new HOV lanes, or a combination of HOV and general purpose lanes. However, implementation would have been five or more years later than the improvements constructed through the public-private partnership.

Exhibit 1-A⁸

Exhibit 1-B

Under Caltrans supervision, the express lanes were designed, built, and are operated by the California Private Transportation Company (CPTC) on land leased from the State. The franchise agreement gives CPTC thirty-five years to operate the toll lanes, after which the facility reverts to full control of the State.

In the meantime, CPTC can set the tolls as the company sees fit, subject to a maximum rate-of-return constraint specified in the franchise agreement. The agreement between the company and the State also requires CPTC to offer an incentive to high occupancy vehicles with three or more persons (HOV3+). Initially, HOV3+ users were toll-free, although they were required to carry transponders like all other users. Starting in January 1998, the HOV3+ toll was set at 50% of the published toll.

Exhibit 1-C

Tolls on the 91X lanes vary hour by hour, to control demand and keep traffic in the 91X lanes operating at free flow. The tolls also reflect the travel time savings of toll lane users compared to travelers on the adjacent non-tolled freeway. The variable toll system is called value pricing. From opening day through summer, 2000, there have been five general toll increases, in addition to the January 1998 change affecting only HOV3+ users.

As seen in Exhibit 1-J, tolls now vary from a low of $0.75, during periods of lowest demand, to $3.75 during the height of the Friday afternoon peak period. All permitted vehicle types pay the same amount, except discounted tolls are paid by HOV3+ users and a few other discounted toll categories.

A "91 Express Club," created in January 1997, permits frequent users to pay a flat $15 monthly fee and receive a $0.75 discount (originally $0.50) on each trip made, regardless of time of day. Belonging to the Express Club provides an overall savings in tolls for persons who use the express lanes more than 20 times per month. Also, it has the effect of eliminating the marginal toll for an off-peak trip. As yet, the Express Club has not attracted many members, about 12% of transponder holders by our estimate.

Partly due to width constraints along the existing freeway median where the toll lanes were constructed, all tolls are collected by Automatic Vehicle Identification (AVI). Only registered customers equipped with suitable transponders are permitted in the toll lanes. The AVI requirement has applied to HOV3+ users from opening day, even though they traveled toll-free.

Through 1999, CPTC had issued about 124,000 of the calculator-sized FasTrak transponders. By that time, an additional 240,000 Fastrak transponders had been issued by the Transportation Corridor Agencies (TCA), which operate the 67-mile network of public toll roads being constructed in Orange County.⁹The transponders, which use a read-write RF tag technology,¹⁰ are manufactured by SIRIT¹¹ (formerly Texas Instruments). They are compatible with California's "Title 21" open standard and may be used on toll facilities throughout California, including San Diego's I-15 HOT lanes, the Golden Gate Bridge, and the State-owned toll bridges in the San Francisco Area. Customer service and electronic toll collection systems for the 91X project were provided by MFS Network Technologies¹².

CPTC does not explicitly require deposits on its AVI transponders; however, a positive cash balance is required on each account. Normally, a credit card user pays $30 to replenish an account whenever the balance falls below $10. Cash customers normally pay $50 to replenish an account whenever the balance falls below $25. In 1997, CPTC began to assess service charges on customers with low activity accounts. Current "Standard Plan" customers pay a $6 per month minimum charge. "Convenience Plan" customers can avoid the monthly minimum by paying a one-time non-refundable $50 fee. ¹³

Exhibit 1-E through Exhibit 1-J show the sequence of toll increases and adjustments made since the 91X lanes opened in December 1995, through the year 2000.¹⁴ CPTC elected to operate the SR 91 facility with a published toll schedule rather than with dynamic tolling, like on San Diego I-15 where tolls are fine-tuned to traffic conditions in real time. While dynamic tolling is within the technical capability of the 91X electronic toll system, CPTC's marketing showed that some potential customers were uncomfortable with the unpredictability of dynamic tolls.

CPTC issues its annual report in the spring of each year. Table 1-I shows the reported financial operating results for each year since opening. Besides the operating expenses shown, CPTC must meet accumulated debt service and provide a rate of return on capital investment.

Table 1-I. CPTC Reported Annual Revenues and Expenses15¹⁵

Year	Total Revenue	Total Operating Expenses
1996	$7.1 million	$6.3 million
1997	$13.9 million	$9.1 million
1998	$20.1 million	$8.7 million
1999	$19.5 million	$9.1 million

CPTC's first annual report stated that, after three months, revenues had reached a level sufficient to cover operating expenses, but excluding debt service and return on investment. In August 1998, the company reported that revenues had reached overall "breakeven," sufficient to cover both operating expenses and debt service.

While financial performance was not directly investigated in this study, the corporate reports indicate that the 91X project has acceptable financial performance, and the project appears poised to yield a favorable rate of return through the life of the project. However, it should be recognized that it is rare for a new urban highway project to have the 91X's unusual combination of relatively low capital costs (less than $3.5 million per lane-mile), large demand, and a favorable institutional environment for quick implementation.

Exhibit 1-D

The long-term financial prospects of the 91X lanes are influenced by the nature and location of competing highway capacity. The nearest major freeway providing independent parallel capacity is State Route 60, running east-west approximately ten miles north of SR 91 (see Exhibit 1-B). Within the SR 91 corridor, the Eastern Toll Road (ETR) competes with the 91X for trips to Irvine and vicinity. (See Exhibit 1-D.) Opening the Eastern Toll Road in October 1998 clearly caused a temporary setback in 91X revenue growth. However, ETR users must use the highly congested SR 91 free lanes in order to cross the Orange/Riverside County Line, while 91X users largely bypass this congestion.

The franchise agreement between CPTC and Caltrans contains a "non-compete" provision through which Caltrans agreed not to make freeway improvements that undermine CPTC's business, unless required for highway safety. During the past few years, this non-compete provision has become a major source of conflict between CPTC, the State, and others, and a solution to the problem has not yet been found. This issue is discussed in detail in Chapter 4.

In addition to the controversy over the non-compete provision of the franchise agreement, problems also arose in connection with CPTC's recent efforts to sell its business. CPTC contacts cite two principal reasons for trying to sell its business: (1) one of the original general partners in CPTC decided that continued participation is not compatible with their core corporate strategy, and (2) tax laws make running the 91X lanes by a non-profit organization more attractive than continued operation as a for-profit business. CPTC's efforts to work with a prospective non-profit buyer were publicly characterized as tainted with conflict of interest, and the potential deal fell through under a cloud of investigation. This issue is also discussed further in Chapter 4.

1.3 Synopsis of Major Conclusions from the May, 1998, Report

The 91X project has developed a growing market for commuters willing to pay premium tolls in order to bypass recurrent congestion on an urban freeway. The fact that the use of the toll lanes is optional and the facility is managed to preserve good levels of service for those choosing to pay the tolls are two key features that clearly have contributed to public acceptance of this project. Travel time savings, improved driving comfort, and perceptions of improved safety are immediate tangible benefits which motivate increasing numbers of travelers to pay the tolls. Traffic diverted to the toll lanes from both the freeway and parallel city streets has improved travel conditions on these non-toll facilities in the short term, further adding to the public acceptance which the project has enjoyed so far.

Although toll revenues do not yet cover total annualized facility costs, the facility's operator predicts financial breakeven by the end of the third year of service (late 1998). Eventual profitability for this project is greatly assisted by its modest capital cost of about $3 million per lane-mile and the lack of competing highway capacity within the corridor.

Impacts on corridor traffic have been generally favorable. Greatly improved travel conditions resulted in a jump in corridor vehicular traffic during the first few months of operation. The greatest amount of this traffic growth was in single occupant vehicles. However, high occupancy vehicle use also grew significantly during the same period, with HOV-2 traffic increasing a little, and HOV-3+ traffic increasing dramatically.

The jump in SOV traffic over the observation period was mostly the result of three distinct effects: (1) traffic returning from parallel city streets, (2) new induced travel for non-work purposes which had previously avoided this severely congested corridor, and (3) continuation of the background SOV growth trend which was present before the express lanes opened. The overall effect of these changes, despite significantly increased volumes of HOV traffic, was a small downward trend in average vehicle occupancy through the first eighteen months of express lanes operation.

Optional congestion-based variable pricing results in highly selective use by travelers. On SR 91, about half the toll lane users choose to use the lanes once per week or less. Data show that the traveler's choice to use the toll lanes is closely related to hour-by-hour variations in travel conditions.

We found that providing the option of nearly congestion-free peak period travel resulted over time in the emergence of a sharp peak period traffic distribution. New toll schedules, first implemented in September, 1997, introduced hour-by-hour toll variations within the peak periods. An unresolved question is whether fine tuning the toll schedules in this manner will result in re-flattening the peak period traffic distribution.

The study produced diverse findings concerning the equitable distribution of project benefits across different traveler groups. While a clear correlation exists between frequency of toll lane use and income level, users from all income groups regularly make use of the facility. The data show that female commuters are about a third more likely than men to make frequent use of the express lane option. It should be noted that commuters in the SR 91 corridor are on average more affluent than the overall urban population of Southern California. Thus, conclusions about impacts across income and gender groups based on this corridor cannot be assumed to apply everywhere.

The express lanes constructed on California State Route 91 have demonstrated that providing new highway travel options, in this case, premium service for a premium price, can win public acceptance and produce significant travel changes.

1.4 Description of the Study Methodology

The overall objective of this study has been to develop information and insights towards improved understanding of travelers' reactions to congestion-based road pricing and to the other innovative features of the 91X toll lanes. To meet this objective, we conducted an extensive program of direct observations, surveys of corridor users, and impact modeling. In all, data collection spanned a time period in excess of five years, from early 1994, approximately a year and a half before opening day, through late 1999. The data collection prior to opening day provided a baseline against which post-opening data were compared.

The specific data collection, analysis, and modeling activities of the study included:

• Observations of traffic conditions at selected sites along the study area freeway network and at some control sites distant from the 91X lanes. These observations include traffic counts, speeds, vehicle types, and vehicle occupancies.
• Observations of traffic volumes on selected ramps and speeds on parallel arterials, in order to estimate the amounts of freeway traffic diversion during congested periods. (Arterial speeds are discussed in the May 1998 report.)
• Observations of ridership on public transportation services and in organized rideshare programs serving the SR 91 corridor. (Rideshare programs are discussed in the May 1998 report.)
• Travel surveys conducted to understand the characteristics of SR 91 peak period commuters and their revealed travel behavior. Some survey participants comprise a longitudinal panel whose behavior was tracked over time, the remainder are cross-sectional observations, mostly current commuters but including a small subset of persons who no longer use the SR 91 corridor. (Travel surveys with public transit riders are documented in the May 1998 report.)
• Use of the travel survey data to calibrate choice models of commuters' decisions about using the toll facilities, on the basis of which we determined price elasticities and travelers' values of time.¹⁶
• Opinion surveys conducted to understand commuters' views about the innovative features of the toll lanes and related public policies, with emphasis on how these opinions changed over time. (Opinion surveys with area businesses and public transit riders are discussed in the May 1998 report.)
• An investigation of trends in accident rates and characteristics and an investigation of traffic operational characteristics, in particular weaving at the entrances and exits of the express lanes. (The weaving observations are documented in the May, 1998, report.)
• An investigation of estimated vehicle emissions in the 91X corridor, compared with modeled emissions for hypothesized alternative lane configurations.

Details on data collection procedures, including scheduling and sample size considerations, and descriptions of our data analysis and modeling techniques are contained in several methodology appendices which appear at the ends of the pertinent chapters.

1.5 Overview of the Rest of the Report

The study addressed a wide variety of issues related to the 91X toll lanes. Our May 1998 report focused on comparisons between periods twelve to eighteen months before and after the toll lanes opened in December 1995. The current report, while documenting most trends all the way back to the start of observations in 1994 or 1995, emphasizes the changes that occurred during the extension period, from June 1997 to 1999.

The rest of this report contains six chapters which cover the major technical areas addressed by the study. They are followed by a concluding chapter which reviews the main findings and issues.

The contents of the remaining chapters are described below.

Chapters 2 and 3 deal with observed impacts on traffic and travel behavior. Chapter 2 documents trends and comparisons related to traffic counts, speeds, observed vehicle occupancies on the corridor highways, and patronage on corridor transit services. Chapter 3 addresses the characteristics of travelers and individual travel behavior, based on the travel surveys conducted from 1995 through 1999.

Chapters 4 and 5 also deal with the data from our survey analysis work. Chapter 4 contains survey findings about trends in public opinions concerning the 91X facility and its principal operational and institutional characteristics. Chapter 4 also contains a section summarizing recent media coverage of the 91X project. Chapter 5 presents results from estimating models of travelers' choices regarding whether or not to use the toll facilities (91X and ETR), as well as choices regarding mode, time of day, and transponder acquisition. Associated price elasticities and values of time are reported.

Chapter 6 presents an analysis of recent collision experience on selected sections of SR 91. A comparison is also made of accident rates on SR 57. A small number of major incidents in or adjacent to the 91X lanes are studied in detail to see if they might be related to the unique operating characteristics of the express lanes.

Chapter 7 provides an analysis of vehicle emissions in the SR 91 corridor for a selected week in March 1998. Emissions for the facility as it exists are compared to modeled emissions for three hypothetical alternative scenarios: the substitution of HOV lanes for the 91X lanes, the substitution of general use lanes, and the "no build" alternative. A critique of the analysis methodology is given.

Finally, Chapter 8 presents our principal conclusions.

Back to Table of Contents

2. Traffic Trends, Driving Conditions, and Transit

2.1 Chapter Introduction

A major part of this study involved monitoring traffic trends on the 91 Express (91X) lanes and on the other transportation facilities serving the corridor. This work took a variety of forms:

• Collection and analysis of 5 minute traffic counts and estimated vehicle speed data from loop counters deployed on freeways and ramps throughout Orange and Los Angeles Counties.
• Coding and analysis of hourly traffic counts for the 91X toll lanes using printouts obtained from Caltrans District 12 in Orange County.
• Compilation and analysis of roadside observations of vehicle occupancies and vehicle types taken usually one day per month at ten observation sites on freeway mainlines and at seven observation sites on ramps.
• Coding and analysis of floating car speed runs on SR 91 and, initially, on two principal arterial routes located parallel to the 91X toll lanes.
• Acquisition and analysis of passenger counts on public transportation services which parallel the 91X, consisting of a single express bus route and a commuter rail line.

Traffic monitoring occurred for over a year prior to the December 1995 opening of the 91X toll lanes, in order to establish baseline conditions, and for more than three years after the opening.

The next section provides a summary of the major findings based on more than four years of observations. Succeeding sections present the related details. The chapter concludes with three methodology appendices which describe the data collection and statistical analysis techniques which were used.

2.2 What We Learned from Traffic Counts and Related Observations

The following are the principal findings from monitoring traffic and travel conditions on the study area freeways and arterials. The location in the text containing the supporting data for each finding is identified.

Overall Traffic Trends and Facility Shares

• The 91X lanes carry a substantial share of the weekday traffic in the SR 91 corridor. After opening day, weekday 91X lane traffic increased steadily until the opening of the Eastern Toll Road (ETR) in October 1998. By September 1998, the total weekday two-way average daily traffic (ADT) using the 91X lanes had reached its peak level at about 33,000 vehicles per day (over 14% of the total weekday SR 91 ADT). Weekday 91X traffic then decreased steadily during the first 6-8 months after the ETR opened. By summer of 1999, the 91X weekday traffic had reached about 24,000 vehicles per day, with no further decreasing trend evident. (Section 2.3, Figure 2-1.)
• 91X traffic in the morning peak direction has been consistently less than in the afternoon peak direction, when congestion in the free lanes is worse. After the ETR opened, that difference increased. 91X lane traffic as well as ETR traffic on Friday afternoons consistently and significantly exceeds all other periods. (Figure 2-3 and Figure 2-4.)
• The trends in 91X weekend traffic have been different from weekdays. The highest weekend ADT values were about 20,000 for a Saturday, reached in August 1998, and about 17,500 for a Sunday, in May 1997. The effect of opening the ETR on weekend 91X traffic was not as great as for weekdays. (Figure 2-2.)
• The weekday ADT on SR 91 (free and toll lanes combined) increased substantially during the months following the capacity increase from opening the toll lanes. The average midweek ADT increased by about 32,600 daily trips between the last quarters of 1995 and 1996, nearly a 17% jump in total daily traffic. Over the same period, midweek 91X lane traffic grew to 24,500 vehicles per day. Between the last quarter of 1996 and the third quarter of 1998, before the ETR opened, the SR 91 total midweek ADT (free plus toll) increased another 3,650 trips (1.6%), while the 91X ADT increased by 6,900 trips to about 31,400. By September 1998, the 91X lanes carried over 85% of the cumulative growth in corridor traffic (31,400 of 36,300) since the toll lanes opened in December 1995. (Section 2.6, Figure 2-22 and Figure 2-23.)
• During its first three months of operation (October-December, 1998), the average midweek ADT on the new ETR toll highway reached 21,200 vehicles per day. This occurred at the same time as the 91X toll lane traffic decreased 3,900 vehicles per day, and the SR 91 free lane traffic decreased 7,400 vehicles per day. The remaining 9,900 vehicles per day is the estimated increase in overall corridor traffic (ETR plus SR 91 -- free and toll, measured at the 91X midpoint). Because the ETR serves some trips between locations entirely within Orange County, only part of this increased traffic crosses the county line. Also, a small portion of the increase may be double-counted. (Figure 2-24.)
• Rough estimates available from ramp counts suggest that just over 20% of the total SR 91 traffic increase (free plus toll) in the first year after the 91X lanes opened (about 7,000 of 32,600 vehicles per day) may be traffic returning to the state highway from parallel city streets. Although traffic congestion on SR 91 increased between 1996 and 1999, the shift of traffic back to the freeway from parallel arterials which accompanied the opening of the 91X toll lanes has mostly continued. (Section 2.7, Figure 2-26.)
• During its second and third quarters of operation, the midweek ADT on the new ETR increased steadily, reaching an average of 33,100 vehicles per day in May-July, 1999. The growth in ETR traffic during this seven month period (+11,900 vehicles per day) was accompanied by a further 5,900 vehicles per day decrease in traffic on the 91X toll lanes. In all, the total decline in 91X traffic by summer 1999 corresponds to about 30% of the total ETR traffic growth during the same period. (Section 2.6, Figure 2-1 and Figure 2-7.)
• Throughout the study period, traffic volumes remained stable in the SR 57/60 freeway corridor located roughly parallel to SR 91, about 16 km. (10 mi.) to the north. In addition, field observations showed no association between opening the 91X toll lanes and changes in HOV traffic using the SR 57/60 corridor. This indicates that the influence of the toll lanes, while locally important, did not induce detectable traveler route shifts at the regional scale. (Section 2.7, Figure 2-25.)
• CPTC reported it had issued about 124,000 transponders by the end of 1999, joining approximately 240,000 transponders issued by the public toll road authorities in Orange County. (Section 2.3.)
• The ETR accepts tolls paid using Fastrak transponders or cash. A consistent 60% of weekday users and 50% of weekend users have used Fastrak since the road opened. (Figure 2-13.)
  
  Adjustments Accompanying Changes in Tolls and Traffic Conditions
  
  
• The first general toll increases which occurred in January 1997 was followed by a significant and permanent reduction in the rate of 91X traffic growth. Subsequent general toll increases, which were less substantial and focused on fine tuning of the hour-by-hour toll schedule, were not followed by visible changes in the overall 91X ADT trend. (Section 2.3, Figure 2-1.)
• There exists a strong correlation between express lane patronage and time of day dependent travel time savings. Over the entire period of observation, the percentage of SR 91 travelers who used the express lanes ranges from about 7% in the midday off-peak, when time savings are minimal, to around 35% in the heaviest PM peak hour when delays to freeway users are worst. The implied values of time for persons who use the toll lanes during the peak hour range from $6 to nearly $14.¹⁷ Since our surveys with peak period travelers show that 91X commuters consistently overestimate their actual time savings when paying tolls, the actual values of time are lower than these estimates. (Section 2.9, Figure 2-35 through Figure 2-37.)
• The increased capacity from adding two new toll lanes in each direction in December 1995 substantially reduced peak period congestion in the entire Orange County SR 91 corridor, giving short-term travel time benefits to all commuters. In the six months after the express lanes opened, the typical PM peak trip delay on the freeway fell from 30-45 minutes to 510 minutes per trip. Subsequently, delays increased gradually to October 1998 when they jumped to the 30-40 minute range following the opening of the ETR. During the first half of 1999, delays decreased somewhat, to about 30 minutes in the PM peak and less in the AM peak. (Figure 2-31.)>
• Time of day distributions of SR 91 traffic show that, in 1996, soon after the express lanes opened and the increased highway capacity no longer constrained demand, the PM peak traffic distribution changed to become much sharper than prior to and shortly after the opening. The reemergence of a sharp afternoon peak at approximately 5:00 PM occurred in the presence of a toll schedule which charged the same amount, $2.75, for the entire period from 3:00 to 7:00 PM. The introduction of a more differentiated toll structure in September 1997, with tolls varying by the hour, had little effect on the sharpness of the overall afternoon time of day distribution for the corridor, or of the 91X traffic specifically. However, in the morning peak, there did occur a small amount of peak flattening accompanying the more substantial hourly toll differences which were implemented during that time. (Section 2.8, Figure 2-27 and Figure 2-28.)
  
  Observations about Ridesharing and Transit
  
  
• Within three months after the SR 91 toll lanes opened, PM peak traffic observations on all lanes of the highway showed a greater than 40% jump in high occupancy vehicles carrying were required to have transponders. (Section 2.10, Figure 2-38.)
• When HOV3+ users were charged a 50% toll in January 1998, about a third of the HOV3+ traffic (about 2,000 vehicles per day) left the 91X lanes, and HOV3+ traffic in the free lanes increased by the same amount. These changes occurred mostly during the shoulder hours and throughout the week, although much less on Friday afternoon. Following these changes, the total PM peak HOV3+ traffic in the corridor remained the same. (Figure 2-17 and Figure 2-38.)
• Through the entire period of observation, from 1994 through 1999, the counts of PM peak dual occupant (HOV2) vehicles remained essentially unchanged. HOV2 users of the express lanes pay the same tolls as SOV users, or half the toll on a per person basis. (Section 2.10, Figure 2-39.)
• The increase in HOV traffic which occurred after the toll lanes opened is measured relative to a small initial base. For example, throughout 1995, before the express lanes opened, HOV3+ vehicles averaged about 4% of the total SR 91 PM peak traffic. After the express lanes opened, the comparatively much larger growth in single occupant vehicle (SOV) traffic produced a small but statistically significant decrease in average vehicle occupancy (AVO). The AVO trend leveled off during the past few years. Notwithstanding the initial reduction in AVO, the counts of HOV2 and HOV3+ commuters increased significantly compared to the conditions which existed previously. (Section 2.10, Figure 2-44.)
• There is no evidence that the opening of the 91X lanes or the ETR impacted the development of public transportation patronage in the corridor, particularly the IEOC commuter rail line. The rail service has competed successfully throughout the observation period for a very small share (<1%) of the commute market. (Sections 2.11 and 2.12, Figure 2-45 and Figure 2-46.)

2.3 91X Toll Lane Traffic - Overall Trends

The SR 91 express lanes attract a substantial share of daily corridor traffic, especially during weekday peak periods. Trends in average weekday and weekend daily traffic on the 91X toll lanes appear, respectively, in Figure 2-1 and Figure 2-2. Toll lane ADTs after July 1997 are all averages of Monday through Friday for two weeks in each month, selected to avoid holidays and be consistent from year to year. Prior to June 1997, in some months two full weeks of data were not available. In these cases, the available data were averaged for each weekday, and then combined with other weekdays to create the necessary ADT estimates.

Since its opening, weekday traffic increased steadily on the 91X lanes until October 1998, when the new Eastern Toll Road (ETR) began competing for some corridor traffic. The weekday average daily traffic (ADT) on 91X toll lanes reached its peak value in Sept. 1998 at about 33,000 vehicles per day (over 14% of the entire SR 91 ADT).Temporary dips in ADT and a decreased growth rate coincide with some of the toll increases implemented between Jan. 1997 and Jan. 1999. These growth rate changes will be examined in greater detail later.

In contrast, after the initial growth period, weekend traffic achieved a plateau by summer 1997, staying generally level until the ETR opened in October 1998. Historical peak values were about 20,000 and 17,500 for Saturday and Sunday, reached in August 1998 and May 1997, respectively. Considering the more erratic trends on weekends, the influence of any ETR competition is not clearly visible. However, for both weekdays and weekends, any 91X traffic losses from ETR competition had apparently bottomed out by June/July 1999.

Figure 2-1

Figure 2-2

Figure 2-1 shows that weekday 91X lane traffic in the AM peak direction (westbound) is consistently less than the PM peak direction, where congestion is worse. After the ETR opened in October 1998, this directional imbalance increased. The increase probably reflects the fact that users of the new ETR impact and are impacted by the bottleneck at the county line much more severely in the eastbound direction than the westbound.

Figure 2-3

Figure 2-4

Another view of the difference in congestion effect appears in Figure 2-3 and Figure 2-4, showing that 91X traffic during the most severe Friday PM (eastbound) peak period consistently and substantially exceeds all other weekday commute periods, while Monday eastbound is consistently a bit less. The corresponding weekend directional ADTs in Figure 2-5 show that the Sunday eastbound traffic in the 91X lanes is consistently less than other days and directions.

Figure 2-5

If we ignore the two-month startup period, the weekday ADT trend shown in Figure 2-1 appears to be composed of three distinct trend lines. Figure 2-6 shows in graphic form the result of fitting linear regressions to those three trends. The R2 values indicate that the three regressions fit the data well, and the three slopes all differ from zero and from each other at the 1% significance level. A Durbin-Watson test showed that serial auto-correlation was not present.¹⁸

The increase of Jan. 1, 1997 raised 91X tolls about 10% in peak periods and 100% off-peak. This first major toll increase was followed by a significant and permanent reduction in the rate of ADT growth. Although the apparent discontinuity in the ADT trend could reflect influences other than the toll change, the possibility that the toll increase is at least partly responsible is consistent with the results of choice modeling, presented in Chapter 5, which show commuters to be moderately price sensitive, such that a 10% toll increase should be followed by about a 7% drop in use of the 91X lanes.

Subsequent toll increases in Sept. 1997 and April 1998 refined the hour-by-hour toll schedule, while increasing the peak tolls about 5% each time. No visible effect in the overall ADT growth trend accompanied these later toll changes.

Figure 2-6

By the end of 1999, CPTC reported that it had issued about 124,000 transponders, supplementing approximately 240,000 additional transponders issued by the public toll road authorities in Orange County through the same period.

The opening of the ETR highway in October 1998 began a 6-8 month period of steady decline in 91X ADT, as many travelers appeared to switch to the ETR route for destinations in Irvine and points south. About midway during this period, on Jan. 31, 1999, 91X peak tolls increased again, although from the ADT trend alone it is impossible to distinguish any separate effect on the rate of ADT decline. It is interesting to note that before the Jan. 1999 increase, 91X peak tolls were in the range $2.85-$3.20, compared to the flat ETR toll of $3.25 between SR 91 and Irvine. After January 1999, eastbound 91X peak tolls became $3.20-$3.35 ($3.50 on Friday), for most hours exceeding the ETR toll, while westbound tolls increased only slightly to $2.90-$3.25, for most hours a little less than the ETR competition.

2.4 ETR and 91X Toll Traffic Comparisons

State Route 241, known as the Eastern Toll Road (ETR), opened in October 1998. This created an unusual opportunity to observe travelers' response to a fixed toll facility operating in partial competition with both a variable toll facility and a congested non-tolled freeway. Due to their different alignments, both the SR 91 and the ETR serve certain origin-destination combinations for which the other highway is not a reasonable choice. However, there are also many trips which are well served by both. For trips between Riverside County and some of the major employment centers of Irvine, the ETR provides a more direct congestion-free route. However, especially for eastbound PM peak traffic, the 91X provides congestion-free travel farther east, bypassing the severe congestion just west of the county line. The network layout is shown in Exhibit 2-A.

Exhibit 2-A¹⁹

The new ETR increased the complexity of the corridor travel patterns in two noteworthy ways. First, the northern terminus of the ETR connects only with the SR 91 free lanes, not the 91X toll lanes, which substantially impacts the bottleneck located between the ETR/91 interchange and the county line (especially eastbound). Second, unlike the 91X lanes, the ETR serves some traffic between locations solely within Orange County, for example, between Yorba Linda and Irvine. Some of these trips would simultaneously appear as reverse commute trips on SR 91 and as peak direction commute trips on the ETR. The locations of our principal count sites (at Imperial Highway on SR 91 and at Windy Ridge on the ETR -- see Exhibit 2-A) would cause such trips to be double-counted in estimates of total corridor ADT. However, examination of the reverse commute traffic on SR 91, before and after the ETR opened (e.g., Figure 2-28), shows no sudden jump in volume, which indicates that the amount of double-counting in the overall corridor ADT estimates is negligible.

This section describes the overall traffic experience for the first ten months of ETR operation, to establish basic comparisons with the 91X and the SR 91 free lanes. All ADT estimates for the ETR are based on data for one week per month, selected to avoid holidays and to match the dates of the SR 91 data used. All ETR counts in this section are from the Windy Ridge Toll Plaza, located on the northern leg of SR 241 just south of its connection to SR 91. These data represent only the portion of ETR traffic connecting to the SR 91 and exclude other ETR traffic connecting to the Foothill/Eastern Toll Corridor and other local interchanges.

Figure 2-7 shows the total and directional ADT trends for the ETR at the Windy Ridge Plaza location during its first ten months of operation. The data are the average weekday ADT, for Monday through Friday. Note that the southbound direction on the ETR corresponds to the westbound direction on SR 91, accommodating the AM peak period commute direction. The figure shows that in its first six months, ETR daily traffic grew to match the 91X (about 30,000 trips per day) and by July 1999, the ETR was carrying more traffic than the 91X had ever carried, on an apparent steady growth trend. Like on the 91X, PM peak (northbound) traffic consistently exceeds AM (southbound) traffic.

Figure 2-7

Figure 2-8 and Figure 2-9 show the time of day distributions of traffic, average for all weekdays. As expected, heaviest use occurs during peak periods. The ETR also has a small but distinct "reverse" commute to jobs in the vicinity of the SR 91 corridor, which the 91X does not serve. Otherwise, patterns are similar to those of the 91X, discussed in Section 2.8.

Figure 2-8

Figure 2-9

Figure 2-10

Figure 2-10 shows the results of superimposing the weekday average daily traffic trends for the ETR and 91X, over the duration of the 91X lanes' existence. The figure shows that the majority of initial weekday ETR trips were not previously paying tolls on the 91X lanes. A jump in daily toll-paying trips of about 19,000 occurred in October 1998 and, subsequently, the positive growth rate of the ETR ADT was about twice the shrinkage rate of the 91X traffic. As seen in Section 2.7, the increase in toll-paying trips after the ETR opened appears to be a combination of new trips in the corridor and previous freeway trips now paying tolls. Some of the new trips on the ETR are probably intra-Orange County, such as between Yorba Linda and Irvine, which cannot easily access the 91X lanes.

Figure 2-11 shows the corresponding directional ADT trends for weekend traffic on the ETR. The lightest day and direction, Sunday northbound, corresponds to the lightest traffic observed on the 91X. However, unlike the 91X, the weekend trend lines are still increasing. Figure 2-12 shows the weekend northbound time of day profile; the southbound profile is similar.

Figure 2-11

Figure 2-12

In addition to fixed tolls, a key characteristic of the ETR is that tolls may be paid with transponders or cash. Figure 2-13 shows the trends in the average percentage of tolls paid by transponder for midweek (Tuesday through Thursday) and weekends (Saturday and Sunday), by direction. Midweek commuters understandably have higher utilization of Fastrak transponders, but not dramatically so. It is interesting to note that these trends are flat through the observation period. Also of interest is that Fastrak use in midweek is consistently a little less for the northbound direction, suggesting greater spontaneity in the commuter's choice to take the toll road for the PM commute.

Figure 2-13

Figure 2-14

Figure 2-15

The final comparisons for the ETR appear in Figure 2-14 and Figure 2-15. Here the directional daily ADT differences and trends are shown. The pattern is similar to the 91X lanes (Figure 2-3 and Figure 2-4), in that the northbound ADT trend for Fridays, corresponding to the most congested PM peak, exceeds all other periods. Of interest is that the Friday afternoon effect appears to be the same magnitude for the ETR and 91X lanes even though, since April 1998, the Friday PM toll on the 91X has been more than at any other time during the week.

2.5 91X Toll Lane Traffic - Full v. Discounted Tolls

An important characteristic of the 91X toll structure is the mandated discount for rideshare vehicles carrying three or more people (HOV3+). During the first two years of operation, HOV3+ travelers on the 91X lanes paid no toll although each vehicle was required to carry a transponder. Starting January 1, 1998 HOV3+ users have been required to pay 50% of the regular toll.

Figure 2-16 shows the trends in 91X lane traffic distinguishing travel direction and toll type. A significant drop in the total daily use of the HOV3+ lanes occurred immediately after 50% tolls were imposed in January 1998. Although the full-toll ADT declined some at the same time, the full-toll traffic returned quickly to its previous trend, while HOV3+ toll traffic remained at the new lower level.

Figure 2-17 shows a larger view of the same HOV3+ trends with three separate regression lines fit to the portions before and after January 1998, and after the ETR opened in October 1998.

Figure 2-16

Figure 2-17

The regressions prior to January 1998 and after October 1998 both fit the data well, while the fit for Jan.-Sept. 1998, although visually close has poor statistical properties probably due to the combination of little data and an apparent up-curving data pattern. Based on the standard error of the regression prediction for January 1998, the drop in HOV3+ lane patronage after imposing the 50% tolls is 2111 vehicles per day, with an estimated standard deviation of 247, a highly significant change.

In addition, the negative HOV3+ trend through the eight months following the opening of the ETR in October 1998 is statistically significant at the 1% level. The negative slope closely tracks the decrease in total 91X traffic (Figure 2-6). From October to November 1998, based on the regression trends, 91X HOV3+ lane traffic fell 2.3%, compared to a 2.4% decrease in 91X traffic in all lanes.

The day-to-day differences in the weekday trends for 91X discounted tolls reveals an interesting difference. These data appear in Figure 2-18 through Figure 2-20. The Monday through Thursday trends mirror the average weekday patterns discussed above. However, the Friday PM (eastbound) direction clearly did not experience as sharp a drop in 91X HOV3+ traffic as other days, even though the Friday AM (westbound) direction did. A t-test applied to the average eastbound HOV3+ traffic comparing the nine months before and after January 1998 shows that Friday's decrease of 484 daily HOV3+ lane trips is statistically significant at the 1% level. The Friday decrease compares to the average decrease of about 700 daily trips for the corresponding Monday and Tuesday-Thursday eastbound traffic. Also, the difference between the decrease on Fridays compared to the decrease on Monday-Thursday, 484 compared to 700, is statistically significant at the 5% level, but not the 1% level.

An important question is what happened to these HOV3+ commuters after January 1998. Did they switch to the SR 91 free lanes? Did they abandon their high occupancy rideshare groups? It turns out that these former 91X HOV3+ lane users mostly remained in 3+ rideshare groups but switched to the free lanes. Also, the majority of the switching from toll to free lanes occurred in the shoulders of the peaks, when free lane congestion is less. This issue is explored in the next section and in Section 2.10.

Figure 2-18

Figure 2-19

Figure 2-20

2.6 Combined Traffic Trends -Free and Express Lanes

This section examines combined traffic trends for the toll facilities and the SR 91 free lanes. The purpose is to quantify and compare changes in traffic over time which are related to the magnitude of traffic diversion among the different facilities. In particular, the section examines the extent to which the rapid growth in 91X and ETR traffic during their respective first few months of operation consisted of new trips or previous trips diverted from parallel facilities.

Figure 2-21 shows the SR 91 midweek ADT (free plus toll) for the period from a year before the 91X lanes opened through January 1999. Unfortunately, due to technical problems, the Caltrans loop data on which the SR 91 free lane counts are based were unavailable after Jan. 1999. The SR 91 free lane counts are from loops located in the vicinity of the Imperial Highway (SR 90) interchange, about two miles west of the mid-point of the toll lanes.

Figure 2-21

The freeway loop counts used for July 1997 through January 1999 are averages of a selected Tuesday and Wednesday each month, chosen to avoid holidays and to match, as much as possible, the dates of loop counts before July 1997. About half the monthly counts for January 1995 through June 1997 are averages for a selected Tuesday, Wednesday and Thursday; the rest are averages of two days (usually Tuesday and Wednesday) and, in a few cases, just one. Usually the counts for the east and west directions are added, however for most of 1995 the westbound loop data were not available, so the eastbound counts were doubled. Unfortunately, despite averaging and the effort to present consistent data from month to month, the loop data tend to be erratic. The monthly averages for 91X are mostly averages of Tuesday through Thursday for two selected weeks; the averages for the ETR represent Tuesday through Thursday for one selected week.

The monthly traffic trend for SR 91 (free plus toll) in Figure 2-21 shows two distinct segments. Before the 91X lanes opened in December 1995, ADTs were mostly in the range 190,000-200,000. Six months after the 91X opened, ADTs had climbed to the 220,000230,000 range, where they remained until the ETR opened in October, 1998. Two regression lines were fit to the data through December 1995 and from March 1996 through September 1998, after the toll lanes opened. These regression lines are also shown in Figure 2-21. Although they visually fit the trends, the regressions have poor statistical properties, with R2 values less than 0.1. The slopes of both regressions are also not statistically different from zero.

Figure 2-22 displays the same ADT data in the form of a quarterly bar chart, in which the annual average midweek traffic (AAMT) also appear as horizontal lines. T-tests show that the jump in AAMT from 1995 to 1996, estimated at 27,144, is significant at the 1% level (the standard deviation of the difference is 9127). Corresponding two-tailed t-tests comparing 1996 AAMT with 1997 and 1997 with 1998 (first three quarters, pre-ETR) show that the AAMTs are not significantly different.

Figure 2-22

Figure 2-21 and Figure 2-22 lead us to conclude that in the past few years the traffic trend on SR 91 has been essentially flat. However, opening the 91X lanes in Dec. 1995 was accompanied by a one-time jump in the SR 91 AAMT of over 32,600 vehicles per day between the last quarter of 1995 and the last quarter of 1996 (a 17% increase). As discussed in connection with Figure 2-26 (Section 2.7), over 20% of the increase in SR 91 traffic during 1996 (7,000 of 32,600) is explained by traffic returning to the state highway from parallel city streets.

Figure 2-23 shows the corresponding midweek AAMT growth for the 91X toll lanes, showing in more detail the nature of the traffic changes after the new toll lanes opened. The quarterly data show that the growth in toll lane traffic lagged the overall corridor traffic growth. By the last quarter of 1996, about 24,500 vehicles per day were using the toll lanes, and 8,100 new trips per day (32,600-24,500) were using the SR 91 free lanes. From late 1996 to the third quarter of 1998, the overall corridor AAMT increased by another 3,650 trips per day (1.6%), while the 91X AAMT increased by 6,900 trips, to about 31,400. By September, 1998, the 91X carried over 85% of the cumulative growth in the overall corridor traffic (31,400 of 36,300).

Figure 2-22 and Figure 2-23 also illustrate that in the initial months after the ETR opened in October 1998, both 91X and overall SR 91 traffic decreased substantially. During the last quarter of 1998, the midweek ADT on the new ETR averaged 21,200 vehicles per day (summed from Figure 2-14 and Figure 2-15). During the same period, the decrease in overall SR 91 traffic is projected to be over 11,300 vehicles per day -- 3,900 from the 91X lanes and 7,400 from the free lanes. The difference of 9,900 vehicles per day (21,200-11,300) is our best estimate of the increase in overall corridor traffic (ETR plus SR 91 -- free and toll -measured at the 91X midpoint near Imperial Highway) which followed the opening of the ETR. These changes in overall corridor traffic are summarized in Figure 2-24.

Note that since the ETR serves some trips between locations entirely within Orange County, not all of the increased corridor traffic crosses the county line. Also, as discussed with Exhibit 2-A in Section 2.4, due to the locations of our count sites it is possible that a small portion of the growth in corridor traffic is counted twice.

During the subsequent seven months of ETR operation, the midweek ADT increased steadily, reaching an average of 33,100 vehicles per day by the period May-July, 1999. This increase of 11,900 vehicles per day (33,100-21,200) occurred at the same time that the midweek ADT on the 91X lanes decreased by 5,900 vehicles per day. By summer of 1999, the cumulative traffic decrease on the 91X lanes was equal to about 30% of the corresponding traffic growth on the new ETR. Unfortunately, the unavailability of mainline loop data prevents direct comparisons for the overall SR 91 facility after January 1999.

Figure 2-23

Figure 2-24

2.7 Diversion from Parallel Routes

Two different issues exist. First, do conditions in the SR 91 corridor cause shifts of traffic to or from other major highways which might be considered competitive with SR 91 for certain trip patterns? Second, do conditions on the SR 91 freeway (and express lanes) cause shifts of traffic to or from parallel arterials in the same corridor?

With regard to the first question, the most reasonable place to look for possible diversion to or from other major highways is on SR 60 and SR 57, which, like SR 91, connects the Riverside/San Bernardino bedroom communities to employment centers in Orange and Los Angeles Counties. To explore this possibility, average midweek daily traffic for SR 57 (Tuesday through Thursday) was calculated for a selected week each month for as much of the observation period as possible. These data appear along with the corresponding SR 91 ADTS in Figure 2-25. Note that the values for SR 57 include an HOV lane and the values for SR 91 include the express lane. Unfortunately, no loop data for SR 57 were available past September 1998.

Despite the erratic loop count data, the SR 57 ADT trend reveals no variations which might be attributed to changing conditions on SR 91. In particular, the trend has no discontinuities around December 1995 when the express lanes opened and when congestion on SR 91 suddenly improved. We therefore conclude that these data do not show the presence of route diversion on a regional scale.

Figure 2-25

Regarding the issue of diversion to local streets, the available data support the case that, shortly after the express lanes opened in late 1995, some commuters who had previously used parallel arterials returned to the SR 91, probably due to its substantially improved travel conditions. The question exists whether that reduced diversion has persisted despite recently worsening freeway congestion. A schematic of the situation appears below:

The principal nearby parallel arterials are La Palma, north of SR 91, and Santa Ana Canyon Road along the south side. Both arterials extend east only to Gypsum Canyon Road, a short distance before the 91X terminus at the Riverside County line. No nearby parallel arterials cross the county line.

Figure 2-26 shows the midweek afternoon peak period traffic trends (averages of Tuesday through Thursday) for available weeks at one of the eastbound on-ramps at Gypsum Canyon and at both eastbound on-ramps at Weir Canyon. These ramps, especially the one at Gypsum Canyon, would be used by drivers seeking to travel on local arterials to bypass SR 91 congestion and then enter the freeway as close as possible to the county line. Although these loop data are erratic and contain gaps, it appears there are three distinct traffic levels for both ramps: prior to December 1995 when the express lanes opened, from January 1996 to March 1998, and from April 1998 to the end of the available data. The premise is that high counts correspond to periods when many drivers avoid the congested state highway to use parallel city streets, and low counts correspond to less such diversion. Figure 2-26 suggests that the use of parallel streets decreased substantially shortly after the 91X lanes opened, and increased again but by a smaller amount during 1998, when freeway congestion increased.

Figure 2-26

To explore the differences in more detail, t-tests were run to compare the average counts for the three time periods. The tests show that the decreased average peak period traffic at both ramp locations from before December 1995 to after December 1995 are statistically significant at the 1% level. The average traffic decreases for the six-hour peak period are 1785 vehicles at Weir Canyon (two ramps) and 1453 at Gypsum Canyon (one ramp). The corresponding increases in April 1998 are 351 and 343 vehicles for Weir and Gypsum Canyon respectively. The Weir Canyon increase is significant at the 5% level but not the 1%, while the Gypsum Canyon increase is significant at the 1% level for a two-tailed test. There is no apparent effect shown in the trend lines associated with opening the ETR in October 1998. (Note that the ETR is not accessible from the Gypsum ramps, but is accessible from the Weir Canyon interchange.)

If we assume that the traffic changes at the second Gypsum Canyon ramp (for which data are unavailable) are the same as at the ramp observed, and that the entire effect at both Weir and Gypsum in December 1995 is due to traffic no longer diverting to local arterials, then the total reduced diversion for the PM peak period is 4690 vehicles (=1785 + 2x1453). If we further assume that reduced diversion in the AM peak is half of the PM (since morning congestion is less severe), this gives a rough estimate for total reduced daily diversion of just over 7,000 vehicles per day, or about 20% of the 32,600 jump in average weekday traffic in the corridor which occurred in the year after the 91X toll lanes opened. Thus, about 80% of the increased overall SR 91 ADT (toll plus free) appears to be new traffic, probably related to the dramatically improved travel conditions. (Section 2.9 discusses the changes in travel conditions in detail.)

The small increase in ramp traffic observed for the period following April 1998 does not appear related directly to the ETR opening in October 1998. The change at Weir Canyon does not appear to be significant, while the change at Gypsum may be related to gradually deteriorating travel conditions on the freeway. In any case, the data provide some evidence that the original shift of traffic back to the freeway from parallel arterials, which accompanied the opening of the 91X toll lanes, has mostly continued.

2.8 Changes in the Time of Day of Travel on SR 91

Besides changing routes, some travelers adapt to congestion by changing the times of day they choose to travel. Although many commuters have little flexibility to change their trip arrival and departure times, other travelers are able to make such changes. Time of day shifts by a fairly small number of travelers can greatly affect travel conditions on a particular highway facility.

Figure 2-27 and Figure 2-28 show a progression of hour-by-hour traffic distributions for SR 91 in the eastbound travel direction. Counts include the free lanes and toll lanes for five typical weeks in successive Februaries concluding in January 1999 (since February data were unavailable). Each curve shows 15 minute loop counts averaged for a typical Tuesday, Wednesday, and Thursday.

The time of day distributions show some interesting effects. Since February 1995, the afternoon peak period on SR 91 has had a constant duration, about five hours long, developing about 2-3 PM and dissipating about 7-8 PM. Prior to the toll lanes opening (Feb. 1995), severe congestion reduced mainline flows, with flow rates during most of the afternoon noticeably less than at the beginning and end of the time period (roughly a bowl-shaped distribution). In February 1996, shortly after the toll lanes opened, congestion had almost disappeared because of the capacity increase, and the bowl shape disappeared, being replaced by a plateau-shaped distribution reflecting the temporal demand pattern which had previously been established.

By February 1997, a sharp peak period temporal demand pattern had emerged, roughly symmetric around 5:00 PM. To enable the emergence of the sharp peak, a substantial amount of the peak period traffic gradually shifted from the free lanes to the 91X toll lanes, as shown in Figure 2-1 and Figure 2-3. This gradual shift established the three-way equilibrium between time savings and tolls and persons' preferred commute time, which appears in February 1997. Approximately the same pattern appears in February 1998. However, by January 1999, the shape hints at the re-emergence of 1995's bowl-shaped distribution, reflecting restricted flow rates from the return of severe congestion.

Sharp peak period demand also appears in the February 1997 and January 1999 distributions for eastbound 91X traffic, shown in Figure 2-29.²⁰ The figure shows basically the same distribution continuing, even though by July 1999 the amount of eastbound traffic on the 91X had decreased due to competition from the new ETR. It should be noted, however, that, despite the lower SR 91 traffic volumes, the additional traffic delivered by the ETR to the bottleneck at the county line caused eastbound PM congestion to become more severe.

Figure 2-27

Figure 2-28

There is no evidence that the more time-sensitive toll schedules which began in September 1997 had any effect on flattening the eastbound PM traffic distribution. In February 1997, a single eastbound toll of $2.75 applied for the entire 3-7 PM period. In January 1999, the more time-sensitive eastbound toll was as follows:²¹

2-3PM	$2.25
3-4PM	$2.95
4-6PM (Tue)	$2.95
4-6PM (Wed)	$3.05
6-7PM	$2.95
7-8PM	$1.60

Figure 2-29

The time of day distribution for westbound traffic on the 91X toll lanes appears in Figure 2-30. A sharply peaked distribution appears in July 1997 and 1998, however the distribution for July 1999 lost its sharp peak following competition from the ETR. Note that after the ETR opened, westbound traffic decreased much more than eastbound. Traffic diverting to the ETR significantly reduced the westbound AM traffic congestion along most of SR 91 adjacent to the 91X lanes. This effect was opposite to the eastbound direction, where ETR traffic merging with the SR 91 freeway led to worse congestion along most of Orange County SR 91 adjacent to the 91X lanes.

Of interest is the possible role of the toll structure for the 91X AM peak westbound direction, which has consistently been more time-sensitive than the PM peak eastbound toll structure discussed previously. In July 1999, AM westbound tolls for Tuesday through Thursday were:

5-6AM	$2.90
6-7AM	$3.00
7-8AM	$3.25
8-9AM	$2.90
9-10AM	$1.95
10AM-12PM	$1.25

Figure 2-30

The AM westbound toll schedule in July 1998 was structured very similarly, all tolls being $0.05 less except for 9-10 and 10-11 and 11-12 AM which were $1.60, $1.10, and $1.00, respectively. In July 1997, a single westbound toll of $2.75 applied for the entire 5-9 AM period, falling to $1.50 for 9-10 AM and $1.00 subsequently. Considering these relatively low toll levels, it seems reasonable to conclude that the large change in the traffic distribution between July 1998 and 1999 probably reflected the influence of opening the ETR, not the changes in tolls.

We conclude that changes made to fine tune the toll structure hour by hour, which began in September 1997, have had a mixed effect on the shape of midweek hourly 91X demand. No visible effect is evident in the afternoon peak, which is not surprising since the midweek toll differences during 3-7 PM, where they exist at all, are minimal (±$0.10). However, differences in the AM peak (5-9 AM) are more substantial (±$0.25-$0.35). Indeed, between July 1997 and 1998, the amount and proportion of AM traffic using the 91X during 8-9 AM clearly increased more than in other AM peak hours. This may reflect the $0.35 toll decrease occurring at 8:00 AM. A chi-square test indicates that the 1997 and 1998 traffic distributions for the 4:00-10:00 AM period are significantly different at the 1% level.

2.9 Travel Speeds and Their Relationship to Express Lane Use

Travel conditions in the SR 91 corridor have varied a great deal during our four and a half years of observation. Before the express lanes opened in December 1995, the commute on SR 91 between Orange and Riverside Counties was one of the state's most congested. In 1996, with the new 91X lanes operating, congestion was greatly reduced as travelers shifted to take advantage of the newly increased capacity. Over time, with increased development and shifts in travel behavior, traffic and congestion in the corridor again increased, and the opening of the ETR in October 1998 suddenly delivered more peak traffic to the county line bottleneck, with worsened congestion, especially eastbound.

Figure 2-31 illustrates this overall historical trend in the form of comparative travel times estimated for the eastbound commute along the 11.3-mile section of the SR 91 freeway between the La Palma over-crossing, just east of SR 57, about 1.5 miles before the 91X entrance, and Coal Canyon Road, close to the county line. These travel times estimates are crude, made by interpolating data from loops located about every two miles along the highway, as described in Appendix 2-B (Section 2.14). Loop speeds are mostly averages over three mid-week days (Tuesday through Thursday) at the mid-points of the indicated time intervals. Despite the crude estimation method, the graph illustrates the long term pattern of congestion along the highway.

In mid-1995, congestion delays at 4-5 PM (travel time minus 11 min. free flow time) were about 30-45 min. In 1996, peak delay had dropped to 5-10 min., increasing gradually until October 1998, when peak delay returned to the 30-40 minute range. By January 1999, delays had reduced some, but remained higher than before the ETR. Although travel conditions worsened with the opening of the ETR, the data suggest that current PM peak delays remain less than in 1995, in both magnitude and duration. A corresponding eastbound graph could not be developed due to inadequate loop data.

Figure 2-31

The location of the congestion shown in Figure 2-31 can be seen in Figure 2-32. These are time-space diagrams developed using the same data. Here, the reciprocal of the slope of each line provides a rough estimate of how speed changes along the route; the steeper the slope, the slower the speed. It is evident that, when congestion occurs, it builds backwards from the county line, near Coal Canyon Road. In June 1995, severe congestion reached as far back as Imperial Hwy.; in 1999, the congestion extended about to Weir.

Figure 2-32

Figure 2-33

As a basis for comparison, data from floating-car runs were obtained from recent work for Caltrans' statewide congestion monitoring program. Figure 2-33 shows the travel time for a series of afternoon peak period runs for SR 91 eastbound, made on Thursday, October 28, 1999. Figure 2-34 shows corresponding westbound runs made the same morning. These data were taken from a 9.5-mile section between Lakeview Ave., located 1.3 miles west of Imperial Hwy. upstream of the location of recurrent afternoon congestion, and Green River Road, located 1.7 miles farther than Coal Canyon Road, a little beyond the Riverside County line.

Figure 2-34

Figure 2-33 and Figure 2-34 show that, on the day examined, the largest observed afternoon peak delay was 14 minutes (subtracting 9 min. free flow time from the values shown) and the maximum observed morning delay was 8 min. The delays indicated in Figure 2-33 are about the same given by the January 1999 data in Figure 2-31, with the exception of the peak readings around 5:00 which, in January 1999, indicate a 30 min. peak delay (when 11 min. free flow time is subtracted from the values shown). The reason for this difference is not known. Figure 2-34 supports the contention that morning delays along SR 91 are much less than in the afternoon, although it should be noted that the heavy congestion which has developed in recent years along SR 91 between Green River Road and I-15 in Riverside Co. is not shown in these displays.

The available data show a strong relationship between patronage in the express lanes and the corresponding savings in travel time. Figure 2-35 through Figure 2-37 show for three different points in time how the percentage of total eastbound afternoon SR 91 midweek traffic using the express lanes varied with time of day and with the estimated trip time saved. As before, the trip times are crude estimates from loop data. Each time saving is calculated as the difference between the estimated trip time and the fastest observed time observed in these data through the section. (This compensates for any systematic biases in the speed values reported by the loops.)

The three figures show quite a consistent pattern. The percent of total SR 91 traffic in the 91X lane tracks the estimated time savings very closely. The three top values for the percent of traffic using the express lanes (35%, 37%, and 38% in 1997, 1998, and 1999, respectively) are similar across a wide range of maximum estimated travel time savings, from 12 min. in 1996 to 29 min. in 1999. It should be noted that the peak PM toll was $2.75 in 1997 and $2.95/3.05 (Tues.-Wed./Thurs.) in both 1998 and 1999.

Figure 2-35

Figure 2-36

Figure 2-37

The implied value of time across these observations varies substantially. In 1997, peak hour travelers paid $2.75 to save a maximum of 12 minutes, implying a time value of at least $13.75 per hour per vehicle. In 1999, travelers paid about $3.00 to save a maximum of 29 minutes, implying a time value of just over $6.00 per hour per vehicle. Of course, these time values assume that loop time estimates are accurate and that travelers accurately estimate their time savings.²²

Surveys with peak period travelers in the SR 91 corridor provide evidence that commuters consistently overestimate their actual time savings when using the 91X toll lanes. See Chapter 3 for details. This implies that actual values of time are less than estimated here. This overestimation of benefits also raises interesting questions with regard to how travelers' behavior might change if they had access to completely accurate real-time information about their true time savings.

2.10 Changes in Ridesharing

The 91X toll lanes were constructed on the site of a previously planned HOV facility. Therefore, it is important to examine the consequences of the 91X with regard to ridesharing. An extensive program of vehicle type and occupancy observations was carried out to obtain data pertinent to this issue. The procedures of this data collection program are described in Appendix 2-A (Section 2.13).

Most findings presented in this section were developed using observations for the PM peak period. The reason for this, as further discussed in Section 2.13, is that afternoon peak observations are more representative of peak flow conditions than morning observations. As it turned out, the scheduling of the afternoon observations coincided more consistently with the actual peak period flows. The AM observations were also made difficult by the very early start of the peak period, which resulted in substantial traffic volumes, especially rideshare groups, passing through the corridor in pre-dawn darkness.

After the SR 91 toll lanes opened, roadside counts showed a greater than 40% increase in the number of peak period HOV3+ vehicles and vanpools in the corridor. This may have reflected the fact that, for the first two years of operation, HOV3+ express lane users paid no toll. Beginning in January 1998, HOV3+ users were required to pay 50% of the regular toll, which was followed by a significant reduction in the total number of daily HOV3+ trips in the toll lanes. (See Figure 2-17 and accompanying discussion.) The question here is whether starting to charge discounted tolls for HOV3+ users adversely affected ridesharing in the corridor overall.

Figure 2-38 shows the year-by-year trend in HOV3+ observations eastbound in all lanes (free and toll) during the 3:30-5:30 PM period, obtained at the Lakeview over-crossing, which is about a mile after the toll lane entrance. These data are from manual counts and therefore subject to a variety of errors; nevertheless, the observations were done carefully and consistently over the years and provide a good relative measure of the trends, even though early and late portions of the peak period were not observed.

Figure 2-38

The jump in HOV3+ traffic after the 91X lanes opened in December 1995 is seen clearly in Figure 2-38. A t-test shows that the increase from the 1994-95 average HOV3+ count of 533 to the 1996-97 average count of 733 is significant at the 5% level, although not at the 1% level. It is evident that imposing 50% tolls on HOV3+ users did not produce a decline in overall HOV3+ use on SR 91. In fact, between 1996-97 and 1998-99, the average HOV3+ count increased from 733 to 905. However, this difference is not significant at the 5% level, probably because there are only seven observation days in 1998-99.

Figure 2-39 shows the corresponding year-to-year trend in observations of two person rideshare groups (HOV2). It is clear in the graph that the total annual average HOV2 counts on SR 91 did not vary from 1994 through 1998. Although the 1999 average HOV2 count appeared to jump dramatically, there were only three observation days in 1999 and the increase from 1996-98 to 1999 is not statistically significant at the 5% level.

Figure 2-39

The data in Figure 2-38 and Figu