Re-Examination of Loss-Time Estimation and Intergreen Time Design for Right-Turn Traffic at Signalized Intersections in Japan

Abstract

The current loss-time estimation and intergreen time design methods in Japan lack sufficient consideration of the characteristics of right-turn traffic, such as right-turner's behavior as well as clearing distance and speed under various phases. Utilizing field data, this paper first examined loss-time estimation method under the permissive-and-protected right-turn (PPRT) and protected-only right-turn (PORT) phasing plans. Results showed that the current method is very likely to over-estimate loss time. Two modifications to the current method for the PORT and PPRT phasing plans, respectively, were then proposed to provide more accurate and sophisticated estimation. Meanwhile, intergreen time design method was examined. It was found that the current method tends to generate unnecessarily long all-red times for right-turn traffic as compared with German method. Thus, it is suggested that the applicability of the German method to Japan conditions needs to be investigated to reduce loss time as well as cycle length.