Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 22
22 decrease from 1.2 to 0.6 min/mi was provided for Ottawa's signal systems and technologies to implement TSP strategies Albert Street to reflect the preferential traffic signal timing for for buses. Through a literature review and case studies a greater buses; and to reflect the platooning effect from an upstream understanding of the state of TSP and how it is employed bus stop, the berth efficiency factor was increased from 2.50 was gained. to 2.75 on Albert Street. In addition, a VISSIM (VISual SIMulation) analysis was From this analysis, the authors suggest several refinements undertaken to evaluate alternative transit priority strategies to the parameters and default values used in TCRP Report 26. along two major bus routes in Burlington, Vermont: Route 15 and the Old North Route. 1. Consideration should be given to increasing the effi- ciency of multiple, on-line berths and recognizing the increased efficiency of platooned operations. VISSIM Results: Route 15 2. Single values of incremental traffic delay for various types and locations of bus lanes, as presented in The following evaluation measures were employed in the Table 3-3 of TCRP Report 26, may not fully reflect Route 15 simulation analysis: bus and car travel time, delay, specific operating conditions. Further latitude is sug- outbound bus waiting time, and side street queue length. gested to better reflect the effects of (1) traffic signals Two TSP scenarios were evaluated: (1) under existing con- set to favor buses, (2) traffic signals located between ditions with a 10-s green extension for the inbound 30 min (as well as at) bus stops, and (3) bus lane blockage. headway a.m. buses, and (2) the headways were changed to 15 min. "A New Methodology for Optimizing Transit Travel time for both buses and autos improved with the Priority at the Network Level," TRB 2008 (20) simulated implementation of TSP, as did delay. However, the bus travel time and auto delay reductions did not prove to This report proposes a methodology to defining the optimal be statistically significant. Bus waiting time represents all the number of exclusive lanes in an existing operational transport times that a bus vehicle is stopped in traffic delay. Outbound network. This study found that most other similar studies focus buses travel in the non-peak direction and do not get priority. only on select arterials when analyzing exclusive lane integra- Although increases in stopped time were seen with the imple- tion and that there is no approach that addresses a network- mentation of TSP, it was not found to be significant. The level analysis. Using bi-level programming that minimizes inbound buses are in the peak direction and receive priority the total travel time, the optimal solution for exclusive lanes treatment. There were significant reductions in the bus wait- within a transportation network can be found. ing time, in the inbound direction, with the implementation of TSP. The analysis of the side-street queue length showed TRANSIT SIGNAL PRIORITY AND that there was no significant difference with the implementa- SPECIAL SIGNAL PHASING tion of TSP. An Overview of Transit Signal Priority, The authors arrived at the following conclusions based on ITS America, 2002 (21) these results (p. 28): This report was the first comprehensive documentation on · A 10-s green extension may reduce bus travel time along what is transit signal priority (TSP), its different compo- Route 15 from 4.6% to 5.8%. nents and applications, and the costs and benefits associated · A 10-s green extension may also reduce bus delay along with TSP. Strategies for planning for deployment of TSP Route 15 from 14.2% to 16.5%. and addressing TSP design, operations, and maintenance · A 10-s extension may also reduce bus waiting time issues are included. Case studies in eight North American ranging from 27.3% to 27.9%. cities [Chicago, Los Angeles, Minneapolis, Pierce County · The other vehicular traffic that moves in the same direc- (Washington), Portland, (Oregon), San Francisco, Seattle, tion as the buses may also experience travel time sav- and Toronto] and cities in Europe and Japan were analyzed ings from 0.3% to 6.3% and a reduction in delay from to identify the benefit and impact of TSP on both transit and 1.1% to 9.5%. traffic operations. The results of these case studies are pre- · These reductions in bus travel time, bus delay, and bus sented in chapter six. waiting time may occur without adversely affecting other traffic. Improving Transportation Mobility, Safety, and Efficiency: Guidelines for Planning and Deploying Traffic Signal Priority Strategies, 2007 (22) VISSIM Results: Old North Route This report was assembled to assist local, regional, and state The following evaluation measures were employed in the jurisdictions in Vermont when considering the use of traffic Old North Route simulation analysis: bus travel time and
OCR for page 23
23 delay to non-transit vehicles. Two TSP scenarios were eval- were near side). The Phase One and Two tests found that uated: (1) under existing conditions with a 10-s green exten- transit bus stop arrival was more reliable with less variability sion for the inbound a.m. buses; and (2) all near-side bus with the use of the TSP system. stops were relocated to the far side. Both scenarios provided reduced travel time as compared Transit Travel Time with the base scenario; however, the reduction found between Scenarios 1 and 2 was not statistically significant. Although In Phase One, eastbound trips experienced shorter travel slight delay decreases were incurred, they also were not found times when TSP was operational, whereas westbound trips to be significant. experienced longer travel times. This was contributed to by the near-side bus stops, which may have had negative impacts The authors report the following conclusions based on on trips with granted priority. In Phase Two, on average, TSP these results (p. 33): saved transit travel time per trip; however, the average tran- sit travel time was longer when TSP was turned off. This is · A 10-s green extension may reduce bus travel time along explained because TSP is only granted for late trips. the Old North Route by up to 7%. · A 10-s green extension coupled with the relocation of all near-side bus stops to the far side suggests that travel Average Person Delay time may diminish, although the results did not prove to be significant. Average person delay was reduced by the SS-RTSP system during Phase One and Two. Comprehensive Evaluation of Transit Signal Priority System Impacts Using Field Observed Vehicle Delays and Stops Traffic Data, June 2008 (23) In Phase One, the TSP system was found to decrease average This study discusses the impacts of the South Snohomish intersection control delay and number of stops at three of the Regional Transit Signal Priority (SS-RTSP) project on transit four intersections; the fourth intersection, although it experi- and local traffic operations by evaluating quantitative field- enced a negative impact, was not found to be significant and observed data and simulation models used to compute mea- did not offset the benefits of the positive impacts at the other sures of effectiveness that could not be obtained from the intersections. In Phase Two, the t-test concluded that with TSP field-observed data. The study was conducted on two corri- implementation there were no significant changes to average dors with the TSP hardware and software already installed. vehicle delay or number of vehicle stops. Early green and extended green active TSP strategies are used in the SS-RTSP system. To measure the effectiveness of the TSP system, primary data were gathered on the follow- Traffic Queue Length ing criteria: transit time match, transit travel time, traffic queue length, signal cycle failures, and frequency of TSP In Phase One, the traffic queue length increased in vehicles "calls"; secondary measures included average person delay per cycle; however, the median value remained constant. In and vehicle delays and stops. Data were collected by Phase Two, the average queue lengths with TSP implemented means of TSP logs, GPS data, traffic controller logs, traf- was not significantly changed. fic video data, and a transit driver log to record reasons for unusual delays; however, the transit driver logs were found to not be accurate in Phase One and eliminated from Phase Signal Cycle Failure Two testing. The study used Structured Query Language (SQL) for data management and was implemented in Microsoft Implementation of TSP did not have a significant impact on SQL Server 2000. VISSIM Version 4.30 was utilized to signal cycle failure in either phase. simulate traffic operations along both corridors. It was an essential tool used to measure average person and vehicle The authors found that the SS-RTSP system provided delays and stops that were not calculable from the field- significant benefits to transit vehicles, whereas the impacts observed data. to local traffic were not significant. The study revealed that with the TSP on, transit vehicles had a higher adherence to Two tests were conducted where TSP was turned off dur- their established schedules and the TSP corridors provided ing week one and on during week two. Phase One was pre- decreased overall person delays. The authors assert that formed on a test corridor approximately 3,600 ft long with "Given that the negative impacts of the SS-RTSP system on three transit routes, four signalized intersections, and seven local traffic was not statistically significant, more transit trips bus stops including three near-side stops. The Phase Two cor- could be given proper TSP treatment, and the frequency of ridor was approximately 5.3 miles long with 2 transit routes, TSP requests could be increased to generate more benefits 13 signalized intersections, and 33 far-side bus stops (none from the SS-RTSP system" (p. 79).
OCR for page 24
24 "Active Transit Signal Priority for Streetcars-- although there is a short length that is normally controlled Experience in Melbourne and Toronto," by a SCOOT System. Nov. 2007 (24) Evaluation of simple green extensions and green recalls This report discusses the application of TSP to streetcar sys- on a 5-s-increment basis within a fixed-time traffic signal tems in Toronto, Canada, and Melbourne, Australia. (Because control environment were conducted on the following tran- Synthesis Report J-7/SA-22 focuses on preferential treat- sit priority strategies. Transit operations within the corridor ments in North America, this report relied on the application were modeled to keep as close to the published schedules as of TSP in Toronto.) The Toronto streetcar system utilizes a possible. detection system consisting of vehicle-mounted transpon- ders and two pavement-embedded detector loops, one for · Base Scenario: No priority. "requests" and another to "cancel." There are two types of · Scenario 1: Priority to express buses traveling along signal priority request that are initiated depending on the Columbia Pike between Dinwiddie and Quinn Streets timing of the request. They are either transit-corridor green (Route 16J). extension or side-street green truncation. · Scenario 2: Priority to regular buses traveling along Columbia Pike between Dinwiddie and Quinn Streets The Toronto streetcar system with TSP experienced "delay (Routes 16 and 24, except route 16J). reduction of 12 to 16 seconds per intersection and streetcar · Scenario 3: Priority to all buses traveling along Colum- travel time savings of 7 to 11 minutes per route" (p. 9). These bia Pike between Dinwiddie and Quinn Streets (Routes travel time savings provide the Toronto Transportation 16 and 24). Commission (TTC) with a "reported annual operating cost · Scenario 4: Priority to buses traveling along cross streets savings of more than $200,000 CAD per route per year, between Dinwiddie and Quinn Streets (Routes 10, 22, which is the direct result of lower fleet requirements (1 to 25, and 28). 2 streetcars) and the associated reduction in hours of labor · Scenario 5: Priority to all buses traveling between and mileage. The TTC found the payback on TSP invest- Dinwiddie and Quinn Streets (p. 8). ments to be achieved in less than 5 years" (p. 9). Although the benefits were noted from the implementation of TSP, other This study concluded that, depending on the specific char- issues were not resolved owing to the characteristics of acteristics of each transportation network, transit priority the streetcar system, its riders, and its operational charac- systems can provide significant benefits to transit vehicles teristics. These issues included frequent bunching of the while not significantly impacting traffic in the network. How- streetcars or excessive gaps, overcrowding of streetcars, ever, in most cases in this simulation the benefits did not and instances where passengers were left behind owing to offset the negative impacts to the general traffic. The most inadequate capacity, and the worst conditions occurred at benefit was found during the midday period and was attrib- stops along high-frequency routes that were located on the utable to lower volumes of traffic and reduced number of nearside of the signalized intersections without dedicated buses requesting fewer priority calls. ROW that had varying passenger demand. "Critical Factors Affecting Transit Signal Priority," "Evaluation of Transit Signal Priority Benefits TRB 2004 (26) Along a Fixed-Time Signalized Arterial," 2002 (25) This article presents a framework for an ideal TSP system and This report looks at implementing TSP along an arterial with a coordinated signalized system. Using the INTEGRATION reviews its impact on traffic operations. Through interviews microscopic traffic simulation model, five alternative prior- of transit engineers and planners and examination of different ity strategies were evaluated on prioritized buses and general transit operating conditions, including congestion levels, bus traffic during the a.m. peak and midday traffic periods along stop location, and bus service level, the different techniques of Columbia Pike in Arlington, Virginia. TSP required under each condition were revealed. These TSP techniques are real-time or fixed-time based control, which The Columbia Pike corridor is a relatively straight, hilly used control strategies such as phase suppression, synchro- four-mile alignment comprised of 20 signalized intersec- nization, compensation, and green recall. tions, a pedestrian crossing and a freeway-type interchange; 6 of the 22 intersections are with major cross streets. Obser- Basic findings of this research were that a real-time control vations revealed that the corridor has directional flow in the strategy has the most potential to reduce delays to non-transit a.m. and p.m. peaks, which are between 6:30 and 9:00 a.m. traffic and is the preferable TSP system treatment. Further- and 4:00 and 6:00 p.m., respectively, and maintains more more, constraints to minimum and maximum greens at the balanced traffic during the midday. For evaluation, fixed- intersection level, using software with a weighing system, time operation was assumed for the length of the corridor, and the implementation of priority to late buses only have