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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
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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).
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"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
