DESIGN CONSIDERATION FOR LRT IN EXISTING MEDIANS: DEVELOPING WARRANTS FOR PRIORITY TREATMENTS

This paper examines current light rail transit planning and design criteria for at-grade crossings and suggests that an alternative criterion be used to determine if priority treatment is justified for LRT at such crossings. Current practice is assumed to be represented by the recently completed UMTA-funded research into light rail surface operations, which suggests that the appropriate evaluation criterion is the impact of light rail on the estimated level of service of the intersection of the arterial carrying light rail and the cross street. This paper, however, argues that the use of the level of service criterion significantly favors the automobile mode over the LRT mode for a wide range of automobile volumes and LRT passenger volumes because it does not consider the volume of people carried by transit. The criterion used to make this determination is the total estimated person-delay induced at the intersection for both automobile users and transit riders. The results suggest, therefore, that at-grade LRT solutions that employ priority measures may be warranted for a wider range of situations than previously deemed appropriate. The design situation used for illustration is the insertion of LRT into an existing highway median. However, the methodology used to evaluate overall intersection performance, both with and without priority treatment for LRT, is applicable to other design situations as well. It is recommended that additional research be conducted by applying the person-delay criterion to other design situations. It is hoped that ultimately a set of warrants will be adopted for LRT priority treatments that are based on the person-delay criterion.