This paper concerns transit quality of service and focuses on reliability. Starting from automated vehicle location (AVL) data collected in a case study, the advantages and limitations of the Transit Capacity and Quality of Service Manual (TCQSM) method for level-of-service (LOS) estimation are discussed. In particular, this method is clear, simple, and easy to use, but sometimes it may lead to inconsistent LOS estimations for three reasons. First, it does not consider the amount of delay but considers only the number of trips that are late. Second, it does not adequately address the effect of early departures on users. Finally, it introduces a fixed tolerance (3 min in advance and 5 min late) around the schedule to consider the trip on time. A new service measure called weighted delay index is proposed; it allows these limitations to be overcome. In this paper, a methodology for its estimation is presented, and new LOS ranges and thresholds for reliability are proposed. Both the TCQSM method and the proposed one have been applied to four routes of the Trieste transit network in Italy. The basic data have been collected through the AVL system during the peak hours of a month. The results have been compared with reference to real data, and it appears that the proposed approach could lead to more graduated LOS estimation because of the higher number of parameters introduced in the new transit service measure.
Samenvatting