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Effectiveness of Disseminating Traveler Information on Travel Time Reliability: Implement Plan and Survey Results Report

CHAPTER 8. TRIANGLE TRANSPORTATION STUDY

As opposed to the other locations, a single round of data collection was conducted in the Triangle study area. Subsequent rounds in Houston and Columbus were conducted using direct outreach through local contacts of the study team. Given that no members of the study team had local contacts in the Triangle area, it was determined that similar outreach would be costly and less efficient.

SITE DEPLOYMENT TIMELINE

Invitation postcards were mailed to potential participants in the Triangle study area on May 15, 2015. The baseline survey was opened on May 18. Qualifying participants were notified by email on June 1, invited to download the smartphone application, and given instructions for recording trips and completing trip diary questions. Phase 1 of the travel study began on June 3. On June 18, Phase 1 participants who had completed at least four recorded trips were invited to continue to Phase 2. Phase 2 concluded on July 6, and participants who had completed at least four trips during Phase 2 were invited on July 7 to take the exit survey. Incentives were distributed by email on July 20 to participants who had completed all steps of the study. Table 34 illustrates the timeline for the Triangle Transportation Study.

Table 34. Timeline of activities for the Triangle Transportation Study.
Triangle (North Carolina) Transportation Study Weekly Timeline of Activities (Date)
May 2015 June 2015 July 2015
Recruitment postcards mailed 15thgray shaded cell: activity took place during this period Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell
Potential participants begin taking baseline survey Empty cell 18thgray shaded cell: activity took place during this period Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell
Participants assigned to treatment groups Empty cell Empty cell 1stgray shaded cell: activity took place during this period Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell
Phase 1 "Welcome" Email Sent Empty cell Empty cell 1stgray shaded cell: activity took place during this period Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell
Triangle Phase 1 Empty cell Empty cell Empty cell 3rdgray shaded cell: activity took place during this period gray shaded cell: activity took place during this period gray shaded cell: activity took place during this period Empty cell Empty cell Empty cell Empty cell Empty cell
Phase 2 "Welcome" Email Sent Empty cell Empty cell Empty cell Empty cell Empty cell 18thgray shaded cell: activity took place during this period Empty cell Empty cell Empty cell Empty cell Empty cell
Triangle Phase 2 Empty cell Empty cell Empty cell Empty cell Empty cell 18thgray shaded cell: activity took place during this period gray shaded cell: activity took place during this period gray shaded cell: activity took place during this period Empty cell Empty cell Empty cell
Exit survey invitation sent Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell 7thgray shaded cell: activity took place during this period gray shaded cell: activity took place during this period Empty cell
Exit survey reminder sent Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell 11thgray shaded cell: activity took place during this period Empty cell
Incentive distribution Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell Empty cell 20thgray shaded cell: activity took place during this period

PARTICIPANT SELECTION AND ASSIGNMENT

For the Triangle region, the study area was defined as the I-40 freeway between U.S. 1 (just west of Raleigh) and just past U.S. 501 (between Durham and Chapel Hill). As shown in the map and table on the following pages, the geographic sample frame included eighteen zip code areas adjacent to I-40 in this area. Unlike the Houston and Columbus study areas, where it was assumed the central city was the largest attractor of regular trips, it was assumed that in the Triangle study area, there were multiple large attractors (Chapel Hill, Durham, Raleigh, and the Research Triangle Park in between) and therefore significant traffic volumes in both directions. However, the geographic sample area selection (based on proximity to the freeway) was consistent with the approach in Houston and Columbus, because there was no known data to indicate whether one attractor was stronger than the others.

Originally, the study team planned to invite a sample of 19,900 addresses to the study (approximately 9 percent of the addresses in the selected area). As previously discussed, this quantity of invitations was planned based on initial predictions about response rates and retention rates throughout the study. However, after reviewing the response from the Houston and Columbus areas in Round 1, the team increased the sample size. Based on revised response rate expectations and available resources, the Triangle address sample was increased to 28,000 (approximately 12 percent of the area population). As with the previous samples, these addresses were randomly selected proportional to the population across the entire area. The sample included all types of residential mailing addresses (single-family houses, apartments, post office boxes, etc.), but excluded "seasonal" and "vacant" addresses. A list of the zip codes used for the invitations is provided in Table 35, while a map illustrating the locations of these zip codes in the region is shown in Figure 27.

Table 35. Triangle sample zip codes.
Zip Code Estimated Number of Households Percent
27709 238 0.1
27510 7,082 3.1
27518 7,659 3.4
27607 8,086 3.6
27278 9,310 4.1
27560 9,331 4.1
27517 10,540 4.7
27514 10,616 4.7
27511 12,719 5.7
27519 12,967 5.8
27516 13,420 6.0
27703 15,875 7.1
27513 15,902 7.1
27612 16,153 7.2
27606 17,035 7.6
27705 18,429 8.2
27707 19,120 8.5
27713 20,596 9.2
Total 225,078 100

Figure 27. This figure shows a map of the zip codes within the Triangle Transportation Study region. They are color-coded (i.e., degree of darkness) to signify population counts.

Figure 27. Map. Triangle sample zip codes geography.

BASELINE SURVEY RESULTS

Table 36 through Table 39 summarize the results of the baseline survey for the Triangle area. Note that all tables include only valid responses, and do not include any responses from participants who were screened out due to infrequent corridor use or lack of a smartphone. Some tables include fewer than 100 percent of qualified participants if the question was skipped by certain participants (for example, participants who reported "never" using the Travel Time Reliability [TTR] information resources in Phase 2 skipped questions about TTR information ratings and satisfaction and instead were asked why they did not use the information).

There was only one round of data collection in the Triangle study area, resulting in 634 complete baseline responses.

Table 36 summarizes how often participants traveled on the main highway in the study area. Compared to Houston and Columbus, Triangle participants traveled on the highway somewhat less frequently. As with Columbus and Houston, participants in the Triangle area were required to travel on the highway at least three times per week to qualify for the study.

Table 36. Number of weekdays typically driven on primary freeway (I-40) in study area, Triangle.
Number of Weekdays Typically Driven on Primary Freeway in Study Area18* Count Percent
5 weekdays/week 359 56.6
4 weekdays/week 111 17.5
3 weekdays/week 164 25.9
Total Baseline Participants 634 100

18* Participants who traveled less than 3 days/week on the primary freeway were not qualified. [Return to 18*]

The Triangle panel age distribution is shown in Table 37. As in the other study areas, the majority of participants were 25 and 55 years old.

Table 37. Respondent age, Triangle.
Respondent Age Count Percent
18-24 42 6.6
25-34 199 31.4
35-44 139 21.9
45-54 121 19.1
55-64 105 16.6
65-74 26 4.1
75-84 2 0.3
85 or older 0 0.0
Total Baseline Participants 634 100

Triangle participants' baseline information also tended to favor smartphone apps (see Table 38).

Table 38. Types of information sources used at least one day per week, Triangle.
Types of Information Sources19* For Familiar Trips: Count For Familiar Trips: Percent For Unfamiliar Trips: Count For Unfamiliar Trips: Percent
Websites 245 38.6 244 38.5
Smartphone apps 378 59.6 360 56.8
Telephone numbers20* 46 7.3 32 5.0
TV 136 21.5 60 9.5
Radio 199 31.4 98 15.5
Built-in GPS device 79 12.5 90 14.2
Portable GPS device 86 13.6 94 14.8
Other sources 17 2.7 11 1.7
Total participants answering 634 -- 634 --

19* Participants could report using multiple sources. [Return to 19*]
20* Generalized question about telephone information use; may or may not include existing 511 services where applicable or other local services (e.g., a state or city toll-free information number). [Return to 20*]

Similar to Columbus, Triangle participants were much more likely to make minor changes (leaving earlier, minor route adjustments) than any other type of change (see Table 39).

Table 39. Types of travel behavior changes made "sometimes" or "frequently" due to traveler information, Triangle.
Types of Travel Changes21* For Familiar Trips: Count For Familiar Trips: Percent For Unfamiliar Trips: Count For Unfamiliar Trips: Percent
Start trip earlier 375 62.3 361 58.5
Start trip later 174 28.9 152 24.6
Make minor route changes 423 70.3 347 56.2
Change to toll road 123 20.4 114 18.5
Completely change route 181 30.1 193 31.3
Change to public transit 18 3.0 12 1.9
Cancel or postpone trip 36 6.0 52 8.4
Telecommute 45 7.5 28 4.5
Total participants answering 602 100 617 100

21* Participants could report multiple changes; some participants skipped these questions because they "never" used traveler information. [Return to 21*]

EXIT SURVEY RESULTS

Table 40 through Table 42 summarize the results of the exit survey in the Triangle study. As shown in Table 40, 111 participants completed the Triangle exit survey.

Table 40. Exit responses by treatment group, Triangle.
Treatment Group Count Percent
Web, Lexicon A 22 19.8
Web, Lexicon B 24 21.6
App, Lexicon A 13 11.7
App, Lexicon B 20 18.0
511, Lexicon A 18 16.2
511, Lexicon B 14 12.6
Total Exit Participants 111 100

As shown in Table 41, the majority of participants thought their study resource was easy to understand and reliable, but that it did not help reduce the amount of travel time they plan for their trips. Similar to the Columbus panel, Triangle participants (see Table 42) appeared to be slightly more satisfied with the TTR information they were provided (as compared to Houston participants). As previously discussed, the exit survey measured participant perceptions of their activities, information use and information satisfaction during Phase 2, rather than objectively observed behaviors or outcomes. The questions included attitudinal statements designed to measure participants' satisfaction with various aspects of the TTR information, as shown in the tables below.

Table 41. Travel time reliability information ratings ("somewhat agreed", "agreed", or "strongly agreed"), Triangle.
TTR Ratings Statement22* Count Percent
The Transportation Study Resource was easy to understand 59 67.8
The Transportation Study Resource was reliable 51 58.6
Transportation Study Resource did NOT reduce the amount of travel time I plan for my trips 64 73.6
Overall, the Transportation Study Resource was useful 37 42.5
The Transportation Study Resource helped me reduce my travel time 13 14.9
The Transportation Study Resource helped me avoid congestion 19 21.8
The Transportation Study Resource reduced the stress of my trip 16 18.4
The Transportation Study Resource helped me plan my trips 26 30.0
Total participants answering 87 --

22* Participants could agree with multiple statements; some participants skipped these questions because they "never" used TTR information. [Return to 22*]

Table 42. Travel time reliability lexicon satisfaction ("somewhat satisfied", "satisfied", or "very satisfied"), Triangle.
TTR Lexicon Category23* Count Percent
Estimated/ approximate travel time 49 56.3
Extra time/ recommended cushion 40 46.0
Recommended/ suggested departure time 33 37.9
Total travel time estimate for most/ majority of the time 45 51.7
Total participants answering 87 --

23* Participants could agree with multiple statements; some participants skipped these questions because they "never" used TTR information. [Return to 23*]

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