A novel transit accessibility measure is proposed following a utility framework to account for the stochasticity in transit services, the effect of real-time information, traffic congestion, and structural features of the transit network, which are disregarded in prior literature. The quantification of accessibility is formulated as a network optimization problem. Through a case study using real-world transit data, the impact of the above features on accessibility was investigated. The results indicate that accessibility is a random quantity exhibiting considerable within-day, day-to-day, and spatial variation across stops, and the disutility from travel time components should be weighted differently for an unbiased estimate. Traffic congestion, represented by the average pace on alternate paths, decreases accessibility linearly. The transit network structure was found to strongly affect accessibility, where the number of available alternative paths had a positive cubic effect, and the degree of overlap among paths had a negative influence on the percentage of improvement in accessibility. Moreover, besides making supply changes, accessibility can be enhanced by providing accurate real-time information on bus arrivals, and the benefit increases quadratically as a function of the out-of-vehicle travel time reduction. The proposed measure, visualization, and analysis methods used, and recommendations made will help transit agencies and planners identify critical locations for interventions to improve transit service accessibility across space and time.
Udhayasekar et al. (Tue,) studied this question.