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21
· Motor vehicles on tracks The lane could operate either in concurrent flow or
· Crossing safety (right-angle accidents) contra flow.
· Poor intersection geometry. 2. Curb bus lane where buses can use the adjacent general
traffic lane for passing around stopped buses. Right
A set of planning guidelines are identified related to design- turns by general traffic may or may not be prohibited
ing roadway geometry and traffic control devices for on- from the curb bus lane.
street LRT: 3. Dual bus lanes with general traffic right turns prohibited.
· Attempt to maintain existing traffic and travel patterns. Adjustment factors were developed to reflect capacity
· Locate the LRT trackway in the median of a two-way increases resulting from skip stop operations and capacity
street, if possible. losses from right-turn traffic conflicts.
· If operating on a one-way street, LRT should operate in
the direction of motor vehicle traffic, with all unsignal- The relationship between bus speeds in the different bus
ized midblock access points closed if possible. lane configurations with stop frequency, stop duration, and
· Two-way LRT operations on one-way streets should traffic signal timing were addressed by use of both field
be avoided. observations and the TRAF-NETSIM model. A look-up table
· If LRT operates within the street ROW, separate LRT is presented identifying bus lane speeds for various stop fre-
operations from motor vehicles by some physical device quencies and dwell times. Speed reduction factors based on
(e.g., raised pavement markets, rumble strips, contrast- the critical bus berth volume/capacity ratio is also presented.
ing pavement texture, or mountable curbs).
· Provide LRT signals that are clearly different from motor
vehicle traffic signals in their design and placement. TCRP Research Results Digest 38: Operational
Analysis of Bus Lanes on Arterials: Application
· Coordinate traffic signal phasing and timing to preclude
and Refinement, Sep. 2000 (17)
cross-street traffic stopping on and blocking tracks.
· Apply traffic signal turn arrows to control left- and This digest presents the results of TCRP Project A-74, which
right-turn movements for motor vehicle traffic that used the bus operational analysis methodology presented in
might conflict with LRT operations. TCRP Report 26 to analyze the performance of six existing
· Provide adequate storage lengths for left- and right-turn arterial bus lanes and recommends refinements to the method.
lanes for motor vehicle traffic, and provide separate turn The methodology of TCRP Report 26 (16) was incorporated
phases. The motor vehicle left-turn phase should follow into TCRP Web Document 6: Transit Capacity and Quality
the LRT phase. of Service Manual (18), and the 2000 edition of the Highway
· Use supplemental interior illuminated signs to supple- Capacity Manual (19).
ment traffic signals to warn motorists making conflict-
ing turns with LRT operations. For this research, data gathered included bus speeds, phys-
· Properly channelize pedestrian crossings to minimize ical site conditions, traffic signal timing, and videotaping
conflicts with LRT operations, using gates and/or barri- of bus travel along the arterial, from the following bus lane
ers where appropriate. locations:
· For on-street operations, load or unload LRT passen-
gers from or onto the sidewalk or a protected raised 1. Fifth Avenue, Portland, Oregon--Dual bus lanes on
median platform and not into the roadway. bus-only street.
2. Sixth Avenue, Portland, Oregon--Dual bus lanes on
bus-only street.
EXCLUSIVE LANES
3. Second Avenue, New York City, New York--Curb
TCRP Report 26: Operational Analysis of bus lane.
Bus Lanes on Arterials, 1997 (16) 4. Albert Street, Ottawa, Ontario--Curb bus lane.
5. Commerce Street, San Antonio, Texas--Curb bus lane.
This research assessed the operation of buses in arterial street 6. Market Street, San Antonio, Texas--Curb bus lane.
bus lanes. The focus was on identifying operating conditions
in which buses have complete or partial use of adjacent lanes, From the observed data the authors were able to suggest
estimating the impacts of adjacent lanes on bus speeds and several refinements to the parameters and default values
capacities, and establishing relationships and procedures for defined in TCRP Report 26 to produce estimates closer to
assessing impacts. The research verified how increasing bus actual bus operations. The authors found that the bus speeds
volumes in exclusive lanes can reduce speeds and how right fell within 20% of the estimated speeds. Slight modifications
turns from or across bus lanes can affect operations. to the speed assumptions resulted in more accurate speed esti-
mations. On Portland's Fifth and Sixth Avenues, delays caused
Three types of bus lanes were analyzed: by intermediate traffic signals warranted increasing the incre-
mental traffic delay from 1.2 to 2.0 min/mi; to account for
1. Curb bus lane where passing is impossible or prohib- blocking of the bus lanes, Second Avenue's incremental traf-
ited and where right turns are permitted or prohibited. fic delay was increased from 2.0 to 3.0 min/mi; an adjusted
