Design of Transit Signal Priority at Signalized Intersections with Queue Jumper Lanes

A queue jumper lane is a special bus preferential treatment that combines a short stretch of a special lane with a transit signal priority (TSP) to allow buses to bypass waiting queues of traffic and then to cut out in front of the queue by getting an early green signal. This paper first proposes a signal control design for queue jumper lanes with actuated TSP strategies and then compares its performance with that of the general actuated mixed-lane TSP. Different design alternatives were evaluated in the VISSIM microscopic simulation. The results show that the proposed TSP with queue jumper lanes can reduce more bus delays than can the commonly-used mixed-lane TSP, especially under high traffic volume conditions. It was also found that a nearside bus stop is superior to the far-side counterpart in terms of both bus delay and overall intersection delay for the proposed design. Introduction The provision of transit signal priority (TSP) on arterial streets is a transit preferential treatment that has received increasing attention in North America. In practice, however, studies have shown that TSP is ineffective during peak hours because buses are not able to bypass the long waiting queues during these hours Journal of Public Transportation, Vol. 12, No. 4, 2009 118 (Nowline 1997; Head 1998; Balke 2000). This paradox has had a limiting effect on the applications of TSP in practice. A special type of bus preferential treatment that has the potential of avoiding this weakness is queue jumper lanes. A queue jumper lane combines a short stretch of a special lane, such as a right-turn lane, with signal priority to allow buses to bypass a waiting queue of traffic and then to cut out in front of the queue by getting an early green signal. Figure 1 shows an intersection with a standard queue jumper lane design. A queue jumper lane can essentially operate like a bus lane at the vicinity of an intersection. However, unlike bus lanes, a queue jumper lane does not take a lane away from the general traffic, making its implementation easier to justify. Instead, a queue jumper lane makes full use of an existing rightor left-turn bay that generally operates under low saturation conditions. In addition, the queue-bypassing capability of a queue jumper lane can avoid the queue uncertainties that limit the effectiveness of mixed-lane TSP, especially under congested conditions. When implemented with TSP, hereafter referred to as the jumper TSP, a queue jumper lane can potentially be more effective than a typical mixed-lane TSP and be more feasible than bus lanes (Zhou 2005, 2006). While the queue bypassing capability of a queue jumper lane is similar to that of a bus lane, the operations of a queue jumper lane are quite different from a bus lane and deserve separate design considerations. Unlike a bus lane, a queue jumper lane requires that buses yield and wait for an acceptable gap to merge back into the main flow downstream. Consequently, the design of jumper TSP, including both the phasing and phase split, is also very different from that of bus lanes or mixed-lane TSP strategies. The objectives of this paper are twofold. The first objective is to propose an actuated TSP strategy and its associated signal control designs for a queue jumper lane. In an actuated TSP strategy, a priority signal is provided only when a request from a bus is detected. The second objective is to evaluate the performance of the proposed queue jumper TSP strategy by comparing it with the general actuated mixed-lane TSP. The next section presents the design of various signal design elements for TSP and queue jumper lanes, including phasing, phase splits, multiple bus services, and coordination recovery and green reimbursement. This is followed by the implementation of the proposed designs in a simulation testbed for a performance evaluation with mixed-lane TSP. The results are then presented and conclusions drawn.