Research on traffic performance of major/minor priority intersections.

This paper describes the state of Polish experiences and guidelines as well as current research activities on the traffic performance of major/ minor priority intersections. Details are given of the basic structure of the existing method, which has modules for (1) input; (2) priority volume; (3) critical gap; (4) service volume and capacity; (5) adjustment. The basic capacity is calculated by considering each minor stream individually in relation to the traffic flow that it must cross and the critical gap, which depends on various parameters of the intersection design. Traffic conditions at the intersection are described in terms of average delay, percentage of stopped vehicles, flow/ capacity ratio and reserve capacity. The paper then discusses recent research activities, which include: (1) a questionnaire survey among users; (2) development of simulation models; (3) empirical, analytical, and simulation studies, including a comparison with chosen methods; (4) improvement and updating of the existing procedure. Some results of a comparison between TRRL's PICADY 2 program and the Polish capacity estimation method are presented in some detail; the two methods are considered to be complementary. The proposed new method maintains the first three modules of the former method, but uses a more limited fourth module, modifies the adjustment module, and adds a level of service module; this method represents an amalgamation of Polish and worldwide results, but it still has several controversial aspects, three of which are mentioned.