User perception of time-based level-of-service criteria for signalized intersections

This study addresses three issues related to level of service at signalized intersections: (1) the appropriateness of using average vehicle delay as a measure of effectiveness for signalized intersections; (2) the appropriateness of the current Highway Capacity Manual (HCM) levels of service for signalized intersections in terms of drivers' time-estimating capabilities and level-of-service (LOS) perceptions; and (3) the factors affecting level-of-service perception at signalized intersections.; Field delay studies were undertaken at three signalized intersections in the Borough of State College, Pennsylvania. A questionnaire of users' perceptions of delay and quality of service was administered in conjunction with one of the three field studies. Further, 98 subjects participated in two laboratory experiments in which they were asked to estimate delay and rate quality of service based on 24 video-tape segments of signalized intersection approaches.; The results provide evidence that the use of average vehicle delay as a measure of effectiveness for signalized intersections is not representative of what individual drivers experience due to the shape and characteristics of the individual vehicle delay distributions. Further, the results suggest that the current HCM methodology for denoting level of service at signalized intersections is not representative of users' delay estimates and quality-of-service perceptions. Specifically, the subjects' delay estimates were inaccurate (especially at lower levels of service), and the analyses indicate that the participants perceived three to four levels of service rather than six.; Thus, it is recommended that (1) the use of individual vehicle delay distributions for signalized intersections be incorporated into the HCM; (2) the current six levels of service by collapsed to four by combining LOS categories A and B and LOS categories C and D; and (3) a method be developed for incorporating two factors, signal efficiency and provision for turning vehicles, into the HCM for level-of-service analysis of signalized intersections.; Future research should focus on assessing users' perceptions of longer delays and oversaturated conditions, as well as how users develop an overall perception of service quality based on multiple trips and their experiences at other intersections.