Decision Support Framework and Parameters for Dynamic Part-Time Shoulder Use:
|Location||Corridor||Length (mi)||Year||Shoulder Used||Max. Speed Allowed||Lane Width (ft)||Notes|
|Idaho Springs, Colorado||I-70 EB||13.0||2015||Left||Variable speed limit||11||Dynamically-priced lane, primarily used in ski season weekends and holidays and some summer weekends. Between US 40/Empire and Idaho Springs. Must be used less than 100 days a year per legislation.|
|Gwinnett County, Georgia||I-85 NB||1.3||2015||Right||Freeway posted speed||11–12||Initially opened with fixed hours of operations, now operated dynamically. Primarily used on weekday afternoons. Auxiliary lane between two interchanges.|
|Ann Arbor, Michigan||US 23||8.5||2017||Left||Variable speed limit (~60 mi/h)||11–12||Between M-14 and M-36 in both directions. Primary used in morning and afternoon peaks|
|Minneapolis, Minnesota*||I-35W NB||3.0||2009||Left||Freeway posted speed||11–12||Priced Lane located at end of managed lane on I-35W northbound between 42nd Street and downtown Minneapolis was routinely opened on weekends and throughout daytime on weekdays. Now removed as part of a major widening project.|
|Fairfax County, Virginia**||I-66||6.5||2015||Right||Variable speed limit||12||Was static from 1992–2015, and dynamic from 2015–2018. From 2015–2018 it was routinely opened in the off-peak direction and on weekends. Extended in both directions from US 50 to I-495 and roadway had HOV lane on the left side. Now removed as part of major widening project|
|Lynnwood, Washington||I-405 NB||1.8||2017||Right||Variable speed limit||13||Between SR 527 interchange and I-5 interchange. Open during core hours in afternoon peak. Core hours begin earlier on Friday year-round and on Thursday in the summer.|
|Chicago, Illinois||I-90||16||2017||Both||Freeway posted speed||12||Shoulders are not routinely opened (except to buses) but can be opened any time for incident management purposes. Between I-294 and Barrington Road in both directions on Jane Addams Tollway|
* I-35W was removed in 2018 as part of major widening projects.
** I-66 was removed in 2018 as part of major widening projects.
|Germany:Baden–Wuerttemberg||A 8||2.6||2013||Stuttgart interchange – Stuttgart–Moehringen (both directions)|
|Germany: Bavaria||A 8||6.1||2005||Hofoldinger Forst – Holzkirchen|
|A 8||9.8||2007||Holzkirchen – Munich–South interchange|
|A 9||18.9||2012–2017||Holledau interchange – Neufahrn interchange (both direct.)|
|A 73||6.8||2008||Forchheim-South – Erlangen–North|
|A 99||11.1||2001–2005||Munich–North interchange – Haar (both directions)|
|Germany: Hessen||A 3||6.7||2001||Hanau – Offenbach (both directions)|
|A 3||2.8||2004/2007||Kelsterbach – Moenchhof interchange (both directions)|
|A 3||4.9||2015||Limburg-North – Diez|
|A 5||11.5||2003||Friedberg – Frankfurt North–West interchange (both direct.)|
|A 5||2.1||2008||Frankfurt interchange – Frankfurt–Niederrad|
|A 5||3.9||2010||Darmstadt–Eberstadt – Darmstadt interchange (both direct.)|
|Germany: Lower Saxony||A 7||20.1||2005||Soltau–Ost – Walsrode interchange (both directions)|
|Germany: North Rhine-Westphalia||A 4||1.0||1996||Refrath – Cologne–Mehrheim|
|A 45||1.9||2014||Schwerte/Ergste – Westhofen interchange|
|A 57||1.9||2011||Cologne–Longerich – Cologne–Bickendorf|
|Germany: Rhineland–Palatinate||A 63||5.6||2011||Saulheim – Mainz–South interchange (both directions)|
|The Netherlands||A1||2.9||2011||Bussum – kp.Eemnes|
|A1||2.8||2011||kp.Eemnes – Bussum|
|A1||4.4||2008||kp. Hoevelaken – Barneveld|
|A2||9.5||2011||kp.Vonderen – Urmond|
|A2||10.2||2011||Urmond – kp.Vonderen|
|A4||0.9||2005||Leidschendam – kp.Prins Clausplein|
|A12||0.5||2005||knp.Prins Clausplein – Voorburg|
|A4||1.5||2011||kp.Nieuwe Meer – kp.Badhoevedorp|
|A10||1.7||2011||kp.Amstel – kp.Nieuwe Meer|
|A4||1.6||2011||kp.Badhoevedorp – kp.Nieuwe Meer|
|A10||2.2||2011||kp.Nieuwe Meer – kp.Amstel|
|A8||0.8||2007||kp.Zaandam – kp.Zaandam|
|A7||4.8||2007||kp. Zaandam – Purmerend-Zuid|
|A7||5.5||2015||Purmerend – kp. Zaandam|
|A8||0.9||2015||kp. Zaandam – Oostzaan|
|A9||3.9||2011||kp. Rottepolderplein – Velsen|
|A9||4.8||2011||Velsen – kp.Raasdorp|
|A9||5.5||2011||Uitgeest – Alkmaar|
|A9||6.2||2011||Alkmaar – Uitgeest|
|A13||3.1||2007||Berkel en Rodenrijs – Delft – Zuid|
|A15||0.5||1999||Papendrecht – Sliedrecht–West|
|A27||3.1||2011||kp.Everdingen – Houten|
|A50||11.7||2006||kp.Waterberg – kp.Beekbergen|
|A50||11.7||2006||kp.Beekbergen – kp.Waterberg|
|A1||8.6||2006||kp.Beekbergen – Deventer – Oost|
|A1||7.6||2006||Deventer – Oost – knp.Beekbergen|
|Bunnik – Veenendaal West
Veenendaal West – Ede
|Ede – Veenendaal West
Veenendaal West – Bunnink
|A12||6.6||2010||Zoetermeer – kp.Gouwe|
|Afrit Gouda – kp.Gouwe
kp.Gouwe – Zoetermeer
Zoetermeer – Zoetermeer–Centrum
|A20||1.8||2006||R'dam Pr. Alexander – kp.Terbregseplein|
|A27||3.1||1999||Houten – kp. Everdingen|
|A27||3.4||2006||kp.Gorinchem – Noordeloos|
|A28||3.9||2004||Zwolle–Zuid – Ommen|
|A28||3.8||2004||Ommen – Zwolle-Zuid|
|A28||2.6||2013||Leusden Zuid – kp.Hoevelaken|
|A28||3.6||2013||kp.Hoevelaken – Leusden Zuid|
|A15||1.9||2015||Trentweg – Welplaatweg|
|A15||1.9||2015||Welplaatweg – Trentweg|
|Denmark||M13||1.2||2016||Hillerød Freeway b/n Junction 8 and Junction 6|
|South Korea||R 1||64.7||Unknown||Gyeongbyu Expressway|
|R 100||1.3||Unknown||Seoul Belt/Ring Expressway|
|R 50||32.9||Unknown||Yeongdong Expressway|
|R 15, 50, 110||11.0||Unknown||Seohaean Expressway|
|R 10, 102||0.8||Unknown||Namhae Expressway|
|R 45||1.1||Unknown||Jungbu Naeryuk Expressway|
|R 55||6.2||Unknown||Jungang Expressway|
|United Kingdom||M42, J3, A7||11||2006||40 km deployed, 400 km of HSR identified by Highways Agency|
|France||A4 – A86||1.4||2005|
|A3 – A86||Unknown||Unknown|
Note: German implementations in Baden-Wuerttemberg, Bavaria, and Hessen have a variable speed limit. The other German implementations have a maximum speed limit of 100 km/h (62.13 mi/h).
D-PTSU = dynamic part-time shoulder use.
This section includes a summary of the operational and safety analysis findings of the dynamic part-time shoulder deployment in the United States and internationally.
A study conducted in Germany reported a 20–25 percent increase in the capacity of a freeway after the implementation of D-PTSU (Geistefeldt J., 2012). The freeway has three general purpose lanes per direction, which the shoulder providing a fourth lane when it is open.
The German Highway Capacity Manual includes the design capacities for freeways with D-PTSU presence internal and external to the urban areas (FGSV, 2015). The design capacities in vehicles per hour (veh/hr) for basic freeway segments with a gradient of less than or equal to 2 percent with the presence of D-PTSU are:
In each case above, the lower capacity value reflects a heavy vehicle percentage of approximately 30 percent, and the higher capacity value reflects a heavy vehicle percentage of approximately 5 percent. The number of lanes reflects the number of lanes in one direction not including a part-time lane on the shoulder.
A study conducted in Denmark reported that the average travel time was reduced by 1-3 minutes on a 9.32-mile section from Allerod to Motorring 3, and 5 minutes on a 7.45-mile section towards junction 6. The traffic volume on the freeway increased after D-PTSU opened, and much of the traffic shifted from local roads onto the freeway (Danish Road Directorate, 2016).
Colorado DOT found there was a 14 percent increase in the throughput, a 38 percent improvement in travel time in general purpose lanes, and an 18 percent increase in the average vehicle speeds across all lanes of eastbound I-70 during high traffic volume periods on the weekends after D-PTSU was implemented (CDOT, 2017).
The study results in this section are categorized into three types based on findings: positive impacts on safety, negative impacts on safety, and challenges regarding the safety performance evaluation of D-PTSU facilities. The majority of safety studies conducted in Germany and the Netherlands indicated that D-PTSU has a positive effect on safety, but studies in the United States have had more mixed results.
A before-after safety study on freeway A3 in the Hessen state of Germany reported there has been a nearly constant crash rate on the D-PTSU segment, whereas fewer upstream crashes, specifically congestion-related (i.e., rear-end) crashes, occurred after D-PTSU implementation (Geistefeldt J., 2012). The crashes were disaggregated into personal injury and property damage only crashes for this analysis. By reducing queuing and increasing speed through a bottleneck area, researchers noted that D-PTSU can reduce upstream congestion-related crashes. This positive safety finding led Hessen to implement D-PTSU on other freeways. (Jones, Knopp, Fitzpatrick, & et. al., 2011).
The majority of safety studies conducted in Germany and the Netherlands indicated that D-PTSU has a positive effect on safety, and U.S. studies have had mixed results.
A study in the Netherlands in 2007 found that D-PTSU reduced crash frequency by 25-28 percent due to the reduction in the upstream congestion. During "low-" and "high-" volume situations, the study from the Netherlands found a D-PTSU lane on the right is more crash-prone than a general-purpose lane. Like the United States, drivers in the Netherlands drive on the right side of the road. However, D-PTSU has safety benefits when there is a "medium" traffic volume (the study does not specify what constitutes high, medium, and low volumes), which has been observed in other countries as well (Rijkswaterstaat, 2007). A later study in the Netherlands noted that traffic on a right shoulder tends to travel more slowly than traffic in general-purpose lanes, but traffic on a left shoulder tends to travel faster than traffic in general-purpose lanes. Despite the higher speeds, the left shoulder tends to have fewer crashes because there are no conflicts with ramp traffic.
A study conducted on a segment of I-66 in Virginia reached similar conclusions: crash frequency dropped by 8 percent after S-PTSU to D-PTSU conversion. This study involved a before-after safety analysis using crash data for 1 year before and after September 2015, when conversion of the facility from S-PTSU to D-PTSU occurred. The segment has a left-side high-occupancy vehicle (HOV) lane and right-side D-PTSU. The crash modification factors (CMFs) for all severities of crashes are:
The CMFs for fatal and injury crashes are:
Some safety studies concluded that there are negative effects in the safety performance between the hours when the part-time shoulder use was open and closed to traffic. An older study on the shoulder use segment on I-66 in Virginia when it was an S-PTSU facility stated that, for the crashes specific to the right shoulder, motorists' behaviors at the merge and diverge areas during adverse light conditions are significant, and there was an increase of about 38 percent in all crashes (Lee, Dittberner, & Sripathi, 2007).
Following the implementation of D-PTSU on I-35W, Minnesota DOT observed that rear-end crash frequency increased in certain roadway sections in the D-PTSU region. Additional analysis showed that the observed increase in the crash frequency was attributed to the change in traffic volume and traffic patterns. The analysis also indicated no direct effect on the likelihood of rear-end crashes due to the operations of the D-PTSU lane (Davis, 2017).
The challenges in evaluating safety performance of those segments with D-PTSU installations include a lack of crash data for evaluation and changes in volume after the D-PTSU opened. Most of the D-PTSU segments in the United States are relatively short and have been implemented in the last few years. Hence, there is limited crash data for identifying the trends in the safety performance of the roadway with D-PTSU. For example, Washington State DOT (WSDOT) reported that in the first 5 months of D-PTSU operations on northbound I-405 between SR 527 and I-5, 11 incidents were reported on the roadway section, including 4 crashes, 6 disabled vehicles, and 1 unclassified incident (Hanson & Westby, 2017). However, this is not enough data to identify the trends in the safety performance of the D-PTSU segment.
Currently, the National Cooperative Highway Research Program is conducting research under Project 17-89, Safety Performance of Part-time Shoulder Use on Freeways. A report on the findings is expected to be available in 2020.
S-PTSU has several traffic operational benefits over a conventional shoulder that is closed to traffic at all times (24/7). These benefits apply to peak congestion hours, typically on weekdays. D-PTSU expands the operational benefits of S-PTSU beyond recurrent weekday peak congestion hours to the rest of the day and throughout the week, including weekends.
D-PTSU expands the operational benefits of S-PTSU beyond recurrent weekday peak congestion hours to the rest of the day and throughout the week.
S-PTSU requires adequate horizontal, vertical, and lateral geometry for traffic operations on the shoulder. The pavement structural section and drainage should be adequate to accommodate the expected traffic loads to the operating agency's satisfaction. S-PTSU reduces the shoulder space available for breakdowns, emergency response, incident clearance, enforcement, crash investigations, and emergency maintenance during the hours of the day when the S-PTSU is open. In addition, when snow is present S-PTSU increases the freeway cross-section that should be plowed and decreases the space available for temporary snow removal storage.
D-PTSU has the same needs and challenges as S-PTSU, extending those same challenges to additional hours and days of the week. In addition, D-PTSU requires a level of traffic management infrastructure and organization much greater than that required by S-PTSU. Agencies should have advanced facility monitoring, maintenance, and operations capabilities on the facility. In addition, facility operations, maintenance, emergency response, and enforcement operations should be well coordinated at all times when the possibility of opening the shoulder exists.
Table 4 provides a list of the potential cost component considerations for D-PTSU and S-PTSU. This list is based on a review of prior Federal Highway Administration (FHWA) documents and outreach to agencies operating D-PTSU facilities.
Part-time shoulder use is one of the strategies addressed by the Tool for Operations Benefit-Cost (TOPS-BC), a spreadsheet-based tool developed by FHWA for benefit-cost analysis. Part-time shoulder use is identified in TOPS-BC as "Advanced Transportation Demand Management Hard Shoulder Running." The user will likely need to modify default unit costs and add inputs to address the specifics of any particular location and application. See the FHWA report on the Use of Freeway Shoulders for Travel for more information on cost-benefit analysis.
|Capital Cost Component|
|System engineering process activities||Typically needed||Typically needed|
|Shoulder reconstruction, widening||Sometimes needed||Sometimes needed|
|Emergency turnout construction||Sometimes needed||Sometimes needed|
|Ramp widening/improvements||Sometimes needed||Sometimes needed|
|Gantry structure spanning roadway or cantilever structure||Typically needed||Sometimes needed|
|Pavement marking modifications||Typically needed||Typically needed|
|Initial training of operations/maintenance personnel, law enforcement, and others as needed.||Typically needed||Typically needed|
|Public outreach/communication campaigns||Typically needed||Typically needed|
|ITS Capital Cost Components|
|Speed sensors, vehicle detectors, travel time indicators||Typically needed||Not needed|
|Camera/surveillance system||Typically needed||Sometimes needed|
|Dynamic/Changeable Message signs||Typically needed||Sometimes needed|
|Overhead lane use control signals||Potentially needed to supplement dynamic/changeable message signs||Not needed|
|Variable speed limit sign system||Sometimes needed||Sometimes needed|
|Controllers||Typically needed||Not needed|
|Communications and power software||Typically needed||Not needed|
|Central hardware and TMC enhancements||Typically needed||Not needed|
|Ongoing Operations/Maintenance Components|
|Additional TMC staff or hours of staffing||Typically needed||Sometimes needed|
|Emergency patrols||Typically needed||Typically needed|
|Upgraded/enhanced level of enforcement||Typically needed||Typically needed|
|Training for operations/maintenance personnel and law enforcement||Typically needed||Typically needed|
|Pre-Opening Sweeps||Typically done in the field or remotely with CCTV||Typically done in the field or remotely with CCTV|
|Maintenance and snow removal similar to general purpose lane||Typically needed||Typically needed|
|Ongoing maintenance costs and replacement costs of signs, structures, pavement marking, etc.||Typically needed||Typically needed, but quantity of equipment may be less|
|Upgraded TMC operations – Integrated operator, first responder, maintenance, and enforcement communications||Typically needed||Sometimes needed|
|Upgraded operating procedures||Typically needed||Sometimes needed|
|Upgraded ITS maintenance program/ongoing maintenance and replacement costs of all ITS-related equipment and infrastructure||Typically needed||Sometimes needed|
CCTV = closed circuit television. ITS = intelligent transportation systems. TMC = transportation management center.
Source: Adapted from FHWA. 2015. Use of Freeway Shoulders for Travel – Guide for Planning, Evaluating, and Designing Part-Time Shoulder Use as a Traffic Management Strategy, FHWA-HOP-15-023, Washington, DC. Tables 8 and 9, available at: https://ops.fhwa.dot.gov/publications/fhwahop15023/index.htm, last accessed February 20, 2019.
Michigan DOT (MDOT) and WSDOT provided general cost estimates from their experiences with D-PTSU. MDOT provided the research team with the bid tab summary report for the US 23 project. The research team also reviewed the 2018 Weighted Average Item Price Report on MDOT's website. MDOT found that for a 17 mile-project on US 23 that used 1/2-mile gantry spacing, the overall ITS system cost approximately $17 million. This translates to roughly $500,000 per gantry location (Palmer, 2018). WSDOT reported an estimated cost of $200,000-$300,000 per location using a signal pole/mast arm system instead of gantries. WSDOT's advanced transportation management software was written and modified for dynamic shoulder lane use in-house and was not included with the estimated costs (Dang, 2018). According to WSDOT's 2010 Congestion Report Gray Notebook Special Edition, a "smarter highways" gantry with variable message and speed signs like those often used with D-PTSU included can range from $650,000 to $900,000 (FHWA, 2018).
The research team also reviewed Virginia DOT's pay item list of statewide averages for May 1, 2016, through June 1, 2018, and the FHWA Intelligent Transportation Systems Joint Program Office Cost database.
Table 5 lists some estimated cost ranges associated with some of the main items necessary for D-PTSU projects. Each project and location will have unique characteristics and design requirements, but these ranges can provide an initial or planning-level viewpoint for agencies as they consider this strategy.
|Gantry structure spanning roadway or cantilever structure||$200,000–$400,000 each||MDOT|
|Speed sensors, vehicle detectors, travel time indicators||$5,000–$20,000 each||MDOT; FHWA-HOP-13-029; ITS-JPO Costs Database for Roadside Detection|
|Camera/surveillance system||$10,000–$20,000 each||MDOT; VDOT; ITS-JPO Costs Database for Roadside Detection|
|Dynamic/changeable message signs||$160,000–$220,000 each||MDOT; VDOT|
|Overhead lane use control system||$30,000–$60,000 each (1-panel system)
$100,000–$170,000 each (3-panel system)
|Variable speed limit sign system||$50,000-$250,000||Rural Intelligent Transportation Systems (ITS) Toolkit, Variable Speed Limit|
|Controllers||$15,000–$25,000||ITS-JPO Cost Database – DMS sign controller (Colorado DOT); MDOT|
CDOT = Colorado Department of Transportation. DMS = dynamic message signs. ITS-JPO = Intelligent Transportation Systems Joint Program Office. MDOT = Michigan Department of Transportation. VDOT = Virginia Department of Transportation.
Note that these cost estimates are based on averages reported in the FHWA JPO Costs Data Base and construction on specific projects completed in Michigan and Virginia over the period 2010 to 2016. They reflect the specific conditions of those designs, localities and periods of time.
United States Department of Transportation - Federal Highway Administration