TRANSIT ROUTE CHARACTERISTICS AND HEADWAY-BASED RELIABILITY CONTROL

Abstract

Previous research has provided a method for improving transit service reliability through headway-based control by using models developed and validated from empirical data. In implementing this strategy, identification of transit routes the characteristics of which can potentially yield significant reductions in passenger wait time is a critical issue. In this paper, several characteristics of the transit route are examined to identify the most appropriate conditions under which headway-based control should be exercised. The paper includes an evaluation of several boarding and alighting profiles that typify ridership characteristics of metropolitan bus systems, sensitivity analyses to determine if small boarding changes or increased volumes affect the benefits of headway-based control, the effects of changes in the weight assigned to passengers detained at the control stop compared with those waiting downstream, the impact of initial headway variation at the route origin, and the effect of parking considerations along a route. The results indicate that profiles with passengers boarding at the middle and alighting at the end of a route produce the most significant savings in passenger wait time when headway-based control is implemented. Improvements in wait-time reduction diminish as more passengers board at early stops and are enhanced as the total ridership increases. Increases in the initial headway variation and amount of parking permitted along a route help deteriorate route reliability and thus improve the effectiveness of implementing a control strategy. The effect of assigning more importance to passengers detained at the control point compared with passengers waiting downstream of control decreases the effectiveness of implementing a headway-based control strategy, as expected. Collectively, the findings are intuitively appealing and suggest preferred conditions under which headway-based control is a viable operating strategy.