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13 For mainline TSP to be most effective, it is important that oped on the intersection approach. The lane must be suffi- transit stops be located on the far side of signalized inter- ciently long enough to allow transit vehicles to effectively sections so that a bus activates the priority call and travels access the lane without blockage if there is an adjoining through the intersection and then makes a stop. For queue through traffic queue. There are two types of queue jump jump signal treatments where there is a designated transit lanes, depending on whether or not signal priority is provided stop at an intersection, the stop could be located either near with the bypass maneuver (see Figure 15). side or far side. With a transit stop near side of the intersec- tion, the operator can trigger the priority call while passen- With Signal Priority gers board and deboard. With this queue jump treatment, a separate, short signal SPECIAL SIGNAL PHASING phase is provided to allow the transit vehicle an early green indication to move into the through lane or bus loading Another signal preferential treatment strategy is to introduce a area far side of the intersection, ahead of through traffic. transit-only signal or added signal phase into an intersection. Typically, green time from parallel general traffic move- This typically would involve provision for a special left-turn ment is reduced to accommodate the special bus signal signal at a particular location to allow transit vehicles to make phase, typically only 3 to 4 s. If there is an optional transit turns onto a cross street. Figure 14 shows a special bus left-turn stop at an intersection, it typically would be located near signal implemented in Portland, Oregon. side. With a near-side stop, passenger deboarding and boarding could occur during a red signal indication. In this situation, a signal priority call would be sent to the con- QUEUE JUMP LANE troller to activate the special signal phase immediately after the closure of vehicle doors. Figure 16 shows a queue jump A queue jump lane is a relatively short lane that is available signal in Portland, Oregon. for transit vehicles to bypass general traffic at an intersection. It is typically associated with bus operations. The transit vehi- cle would enter into a right- or left-turn lane (the right lane Without Signal Priority being most common), or a new exclusive transit lane devel- If signal priority is not provided, a transit vehicle could still use a right-turn lane or right-side separate lane to bypass a general traffic queue, but then proceed under the normal through sig- nal phase into a far-side bus zone or bus pullout. In this case, the bus stop would typically be far side of the intersection. Figure 17 shows typical "Except Buses" signage associated with a bus bypass lane application. CURB EXTENSIONS Curb extensions (also known as bus bulbs) can serve as tran- sit preferential treatments on urban streets. This concept, typically applied with bus and streetcar operations, involves extending the sidewalk area into the street so that transit vehi- cles do not have to pull out of the travel lane to serve passen- gers at a stop. This eliminates the "clearance" time associated with transit vehicles at the curb at a stop waiting for a gap in the general traffic stream to pull back into the through lane. There can be significant travel time savings to transit when applied over a series of transit stops along a route. Curb extensions can be applied far side or near side of inter- sections (see Figure 18 for near-side treatments), or at mid- block (see Figure 19). To develop a curb extension, either a parking lane or loading zone must be available to develop the expanded passenger waiting area. This treatment typically requires the removal of two or more parking spaces or a load- ing zone to provide sufficient length to develop the curb exten- FIGURE 14 Special left-turn signal for buses--Portland, Oregon sion. Curb extensions can also provide space for landscaping (Source: Kittelson & Associates, Inc.). and passenger amenities such as benches and pedestrian scale
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14 FIGURE 15 Bus queue jump signal/bypass lane concept [Source: TCRP Report 118 (5 )]. FIGURE 16 Queue jump signal--Portland, Oregon [Source: FIGURE 17 "Except bus" signage used in bypass lane TCRP Report 118 (5 )]. operations [Source: TCRP Report 118 (5 )].
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15 FIGURE 18 Near side curb extension placement [Source: TCRP Report 65 (8 )]. Before After Bus pulls to curb at bus stop: must wait for gap Curb extended into parking lane, bus stops in in traffic to proceed. travel lane; more curbside parking available. P P BUS BUS STOP STOP FIGURE 19 Mid-block curb extension concept [Source: TCRP Report 118 (5 )].
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16 lighting, assuming such features do not restrict intersection sight distance for traffic. Curb extensions also reduce the pedestrian crossing distance across the street on which the transit vehicle is operating. Curb extensions are normally applied when traffic volumes on an urban street are relatively low (up to 500 vehicles per lane), there are low-to-moderate right-turn volumes, and there are at least two lanes in the particular direction, which would allow general traffic to circumvent a stopped transit vehicle. This is particularly important with any far-side extensions, such that general traffic would not back up into the prior intersection. Curb extensions typically would not be located where there are high right-turn volumes, particularly truck movements, given the relatively tight curb radius associated with such treatments. FIGURE 20 Curb extension treatment--Portland, Oregon Figure 20 shows a curb extension treatment developed in [Source: TCRP Report 118 (5 )]. Portland, Oregon.