Guidelines for the Planning and Deployment of EVP and TSP

1. Guidelines for the Planning and Deployment of EVP and TSP Presented by: Hesham Rakha Associate Professor, Civil and Environmental Engineering Director, Center for Sustainable Mobility Virginia Tech Transportation Institute

2. OverviewWhat is EVP? • Emergency Vehicle Preemption (EVP) entails: • Preempting a traffic signal controller by providing a green phase for an emergency vehicle • Conditional on the absence or completion of pedestrian phases • May involve either green extension or red truncation • Ignores traffic signal coordination requirements (maintaining cycle length) H. Rakha

3. OverviewWhat is TSP? • Transit Signal Priority (TSP) entails: • Providing preferential treatment to transit vehicles to facilitate their flow • TSP requests may be conditional on: • Absence of a pedestrian phase • Presence of a green interval • Prescribed level of transit vehicle occupancy • Degree of bus lateness • Level of congestion at signalized intersection H. Rakha

4. PlanningInstitutional Issues • Institutional issues include: • Identification of important stakeholders • Assessment of local EVP and TSP needs • Formulation of local EVP and TSP objectives and requirements • Compile a document that provides a structured approach to aid in addressing these institutional issues and local needs H. Rakha

5. PlanningPre-Deployment Impact Analysis • Stakeholders should conduct a local impact analysis • Assess the anticipated consequences of alternative EVP and TSP strategies under consideration • Consequences may be the impact on traffic flow and vehicular and pedestrian safety • Empirical analyses and the use of microscopic traffic simulation • CORSIM, INTEGRATION, VISSIM, Paramics, & AIMSUN2 H. Rakha

6. EVP EvaluationsState-of-Art Evaluations • EVP can produce significant savings in emergency vehicle travel times • Response times reduced by • 14-23% in Denver, Colorado (1978), • 50% in Addison, Texas (BRW, 1997), • 16-23% in Houston, Texas (Traffic Engineers Inc., 1991) H. Rakha

7. EVP EvaluationsState-of-Art Evaluations • System-wide impacts: • Increase non-EV vehicle delay by less than 3% along Route 7 (Bullock et al., 1999) • Multiple preemptions result in significant delay increases (Nelson and Bullock, 2000) • Travel time increases decrease from 12.2% over normal travel times after 15 minutes to 3% over normal travel times 60 minutes later (McHale and Collura, 2001) H. Rakha

8. EVP EvaluationsState-of-Art Evaluations • Between 1994 and 2000: • More than 643 EV crashes involving one or more fatalities nation-wide (USDOT, 2002) • EVP can decrease the number and severity of crashes: • 70% reduction in accident rate at 285 traffic signals in St. Paul, MN between 1969 and 1976 • Louisell et al. developed a conflict analysis tool to quantify the likelihood of crashes H. Rakha

9. EVP EvaluationsState-of-Art Evaluations H. Rakha

10. Transit Priority EvaluationsRoute 1 Network Configuration • US Route 1 arterial in Fairfax, Virginia • 8.1 mi over 27 signalized intersections • Total demand of 16,000 veh/peak period • Fixed-time time-of-day signal timings H. Rakha

11. Transit Priority EvaluationsField Evaluation Results • The findings of the field evaluation study are summarized as follows: • The study demonstrated that a WAAS-enabled GPS receiver is an effective technology in the evaluation of TSP. • The study found that dwelling times are not affected by TSP operation. • Green-extension TSP may reduce delay to transit vehicles at intersections (3 to 6% reductions but were not statistically significant). • The benefits provided by TSP are highly dependent on the level of congestion and can be maximized under moderate-to-low levels of congestion. H. Rakha

12. Transit Priority EvaluationsModeling Evaluation Results • TSP has no impact on transit vehicle travel times, system-wide travel times, and side street queues. • An increase in Route 1 demand results in increases in system-wide dis-benefits of TSP. • Maximum system-wide increase in delay is minimal (less than 1.37%). • An increase in the side-street demand does not result in any statistically significant system-wide disbenefits. • An increase in transit vehicle frequency results in reductions in bus delays by up to 3.20%. • No system-wide benefits are observed when TSP is operated. • TSP operations are impacted by the location of bus stops: • Near-side bus stops result in a 2.85% increase in delay, • Far-side bus stops result in network-wide delay savings of 1.62%. H. Rakha

13. Transit Priority EvaluationsColumbia Pike Network Configuration • Columbia Pike arterial in Arlington, Virginia • 1.2 mi arterial carrying 26,000 vehicles per day • 16 SCOOT and 5 fixed-time intersections N H. Rakha

14. T=0 T=T+1 N Transit Vehicle Detected? Y Y Priority Provided in Cycle? N Other Calls for Priority on Y Conflicting Approaches? N Truncate Conflicting Phase N N Y Green Displayed > Minimum?` Subject Approach Green? Y Subject Green Requires N Extension? N Y Y Phase Exceeds Extend Phase by 5s Set to Maximum Maximum? H. Rakha

15. Transit Priority EvaluationsSummary Results • Impacts on prioritized vehicles: • Delay, stops, fuel consumption, and emission reductions for all strategies considered • No clear impact on travel time variability • Impacts on general traffic: • AM peak: Negative impacts due to high congestion at a few intersections • Midday: Negligible negative impacts as a result of spare signal capacity • Increasing negative impacts with increasing number of prioritized buses • Difficult for traffic along prioritized routes to benefit from priority due to differences in traffic and transit behaviors H. Rakha

16. Transit Priority EvaluationsSummary Results • Effect of adaptive traffic signal control • Transit vehicles: similar benefits under all types of signal control strategies • General traffic: less negative impacts under adaptive control as system is able to automatically adjust to temporary queuing or congestion caused by transit priority H. Rakha

17. TSP General Conclusions • Rakha and Zhang (2004) concluded the following: • Generally, TSP provides benefits to transit vehicles that receive priority. • Traffic demand increase results in larger system-wide dis-benefits. • Bus frequency increase results in larger system-wide dis-benefits. • Bus arrivals on • heavily congested approaches may result in system-wide benefits if conflicting approaches are not congested. • lightly congested approaches may produce significant system-wide dis-benefits if conflicting approaches are heavily congested. H. Rakha

18. TSP General Conclusions • Transit vehicle arrivals during the early phases produce minimum disruptions to the general traffic • The system-wide benefits of TSP are highly dependent on the optimality of the base signal timings. • Transit vehicle dwell times at near-side bus stops can have significant system-wide impacts on the potential benefits of TSP. H. Rakha

19. Implementation RecommendationEconomic and Financial • EVP and TSP projects may: • Have short life span, lower upfront costs, and higher operating costs than traditional physical infrastructure projects • Traditional B/C may not be appropriate: • Multi criteria analysis should be used (Leviakangas and Lahesmaa, 2002). H. Rakha

20. Implementation RecommendationProcurement • Identification of system objectives • A clear understanding of the project scope can reduce future misunderstandings • RFP preparation • A single integrator should be responsible for the design, procurement of components, system integration, installation, testing, and user training H. Rakha

21. Implementation RecommendationSystem Installation • These systems have 3 major components: • In-vehicle subsystems • Emitter, power system, and microprocessor • May also include GPS and APC devices • Road-side subsystems • Detectors mounted in the vicinity of traffic signals, microprocessors, and communication systems • Center subsystems • Contractor should be responsible for quality control of all subsystems H. Rakha

22. References • References: • Ahn K., Rakha H., and Collura J. (2006), Evaluation of Green Extension Transit Signal Priority Strategies using Portable GPS Receivers, Transportation Research Board 85th Annual Meeting, Washington D.C., CD-ROM [Paper 06-0641]. • Rakha H. and Zhang Y. (2004), Sensitivity Analysis of Transit Signal Priority Impacts on Operation of a Signalized Intersection, Journal of Transportation Engineering, Vol. 130(6), pp. 796-804. • Dion F., Rakha H., and Zhang Y. (2004), Evaluation of Potential Transit Signal Priority Benefits Along a Fixed-Time Signalized Arterial. Journal of Transportation Engineering, Vol. 130(3), May/June, pp. 294-303. • Chang J., Collura J., Dion F., and Rakha H. (2003), Evaluation of Service Reliability Impacts of Traffic Signal Priority Strategies for Bus Transit. Transportation Research Record 1841, pp. 23-31. • Electronic documents: www.filebox.vt.edu/users/hrakha. H. Rakha