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· Traffic agencies indicated they were most supportive of street travel lane, appears to be driven by answers to the fol-
TSP, queue jump and bypass lanes, exclusive lanes, and lowing three questions:
limited stops, and least supportive of median transit-
ways, special signal phasing, and curb extensions. 1. Is the transit demand high enough to warrant service so
frequent that exclusive transit lanes will be well-used
and even self-enforcing?
WARRANTS, COSTS, AND IMPACTS OF TRANSIT
2. Is there adequate roadway right-of-way available to
PREFERENTIAL TREATMENTS
develop a median transitway or added traffic lanes that
This synthesis report presents documented information on the could be dedicated to transit use?
warrants, costs, and impacts of different transit preferential 3. Will the development of exclusive transit lanes still
treatments. Most of this information comes from previous allow adequate local access in a corridor, recognizing
NCHRP and TCRP research efforts, in particular NCHRP that median transitways block mid-block and unsignal-
Report 155: Bus Use of Highways: Planning and Design ized intersection left-turn access, and curbside transit
Guidelines (2), TCRP Report 26: Operational Analysis of Bus lanes have to share the lanes with local driveway move-
Lanes on Arterials (16), TCRP Report 90: Bus Rapid Transit-- ments and right turns at intersections?
Volume 2: Implementation Guidelines (4), TCRP Report 100:
Transit Capacity and Quality of Service Manual (3), and TCRP Median transitways on urban streets to date have largely
Report 118: Bus Rapid Transit Practitioner's Guides (5). been applied to light rail service. This application is prev-
alent, as light rail over an entire corridor has a greater
NCHRP Report 155 identified both general traffic and tran- investment than a bus facility and that the maximum travel
sit volume thresholds for exclusive lane and signal priority speed and on-time performance that can be achieved with
treatments for buses. A similar set of thresholds for light rail an exclusive transitway is critical in making LRT a cost-
transit (LRT) and streetcar operations has not been identified. effective investment. On one-way streets, however, LRT
The transit and traffic agency survey responses from this has operated curbside, to facilitate pedestrian access to
synthesis identified a set of criteria used to establish the stations.
need for certain preferential treatments, but in general spe-
cific warrant values were not identified. Over the past 20 years, there have been only two appli-
cations of a median busway in North America, the original
For the different transit preferential treatments, both capi- busway on Road No. 3 in Vancouver, British Columbia, and
tal and operating and maintenance costs have been identified.
the new median busway at the west end of the Euclid Corri-
The synthesis revealed that there can be a significant range in
dor in Cleveland. The decision to develop the median facil-
costs based on the technology deployed (related to signal
ity in Cleveland was driven by the need to preserve on-street
modifications) and the extent of physical roadway improve-
parking in Cleveland close into downtown.
ments (mainly in the development of exclusive transit lanes).
Documentation of impacts of different transit preferen- In evaluating the feasibility of developing dedicated tran-
tial treatments has focused on the travel time savings and sit lanes in a street right-of-way, the costs and impacts of
improved on-time performance to transit. The extent of the such treatments must be evaluated. Figure 55 presents a flow
benefits is associated with the degree of application and the chart from TCRP Report 118 that identifies the different fac-
level of congestion associated with general traffic operations tors that have been considered and their relationship.
on the street. There has been less documentation on the impact
to general traffic operations of different treatments, although it The decision where to locate a bus lane if developed
has been identified in some studies that TSP can have a negli- outside of the median, and the hours of operation of the
gible impact on general traffic operations if applied where traf- lane for exclusive use by buses, will be dependent on the
fic operations are under capacity. Also, converting a general desired length and limits of the exclusive lane, the impor-
traffic lane to an exclusive transit lane can cause increased tance of keeping on-street parking all day, and the general
congestion in the remaining general traffic lanes or diversion traffic volume pattern on the street. If on-street parking can
to parallel streets if the exclusive transit lane and level of tran- be eliminated during peak hours, then locating a bus lane
sit service cannot sufficiently attract former automobile users in the parking lane is doable and there are several success-
to take transit to lower overall traffic volumes. ful applications in North America. Typically, such lanes
operate as transit lanes for 2 to 4 h during the weekday a.m.
and p.m. peak period. Operating a bus lane in the travel
DECISION-MAKING FRAMEWORK
lane next to a parking lane, or "offset" lane, is desirable
Exclusive Lanes where on-street parking has to be maintained at all times.
Contraflow lanes typically are only applied for short lengths,
The decision to develop dedicated transit lanes within a street and in downtown areas, and operate all day as exclusive
right-of-way, whether in a separate median transitway or in a transit facilities.
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FIGURE 55 Evaluation process for dedicated transit lanes [Source: TCRP Report 118 (5 )].
Transit Signal Priority Queue Jumps and Bypass Lanes
TSP priority can be applied as a separate preferential treat- If TSP is not possible to apply at an intersection given (1) over-
ment or in combination with other treatments, such as exclu- all traffic conditions, (2) the absence of an AVL or APC system
sive lanes and stop consolidation. Several questions must be to allow for conditional priority if that is the only acceptable
addressed in deciding if and how TSP is to be implemented treatment, and/or (3) the need to have a near-side transit
in a transit corridor: stop, then a queue jump signal or bypass lane into a far-side
stop could be an option. To make this decision, the following
· Are traffic conditions and transit volumes along a corri- questions can be asked:
dor currently within or projected to be within the "opera-
tionally feasible" range to successfully implement TSP? · Is there a right-turn lane (or left-turn lane) available to
· Can TSP be implemented without creating unaccept- serve as a transit bypass lane?
able congestion on cross streets? · If not, is there an ability to cost-effectively develop within
· Is it possible to implement an extended TSP treatment the street right-of-way a separate auxiliary bypass lane for
along a corridor with a median tramway or exclusive transit vehicles?
transit lanes and, if so, would it provide added benefit to · Whether or not a turn lane exists or a new auxiliary lane
warrant the added cost? could be developed, is the lane long enough to allow
· Can transit stops be located on the far side of an inter- transit vehicles to bypass the through traffic queue on
section, or mid-block, so that effective TSP can be the intersection most of the time, particularly during
provided?
peak periods?
· Is the existing traffic signal control system capable of
· Can the bypass lane be developed so that transit vehicles
accommodating TSP, or are signal hardware and/or soft-
would not conflict with turning traffic?
ware modifications needed?
· Can the intersection signal timing be modified to take
· Will automatic vehicle location (AVL) or automatic
away a few seconds of green time from the main street
passenger counter (APC) be integrated with transit vehi-
through traffic to give to a queue jump signal?
cles, which will dictate whether conditional or uncondi-
· Is there a far-side pullout or zone available to accept
tional TSP can be applied?
transit vehicles going through the intersection using a
Figure 56 presents a flow chart, also presented in TCRP bypass lane if a far-side stop is desired?
Report 118, that provides a decision framework for identify-
ing the warrant and configuration of implementing TSP at an Given their potential costs and impacts to general traffic,
intersection or along a corridor. queue jump signals and bypass lanes can be developed to
