Guidelines for the Planning and Deployment of EVP and TSP

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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

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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)

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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

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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

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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

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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)

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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)

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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

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EVP EvaluationsState-of-Art Evaluations
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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

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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.

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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.

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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

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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

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Transit Priority EvaluationsSummary Results
No TSP TSP
Fixed-time ? ?
Adaptive ? ?

• 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

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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.

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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.

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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).

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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

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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

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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/hra
  kha.