New Model for Secondary Benefits of Transit Priority

The case for transit priority can be substantially enhanced if direct passenger travel time benefits are supplemented by secondary benefits, such as mode shift (from automobile drivers) and operating fleet resource savings (due to running time improvements). Although these effects have been theorized in previous research, no quantitative evidential basis has been established. As part of a wider international research project aiming to develop new methodologies to plan and optimize the design of transit priority schemes, actual evidence of transit priority impacts is used to fill this gap and expand on previous theoretical models. Evidence of mode shift effects suggests that transit priority can generate mode shift from automobile drivers at levels of travel time savings much lower than those suggested in previous theoretical models. A strong statistical link between the percentage of travel time savings resulting from transit priority and reductions in automobile driving was established (R-2=.76). Evidence shows that transit fleet savings resulting from priority schemes can occur at much lower levels of travel time savings than previously suggested, as long as transit route lengths and headways are reasonably short. Analysis results suggest that savings in fleet resources will continue beyond the thresholds suggested in theoretical models. A revised theoretical model of the secondary benefits of transit priority is suggested; it reveals that benefits are cumulative and generally higher than previously suggested. Areas for future research are recommended.