The computational methodology for signalized intersections is based on an iterative process including the following functions for each calculation cycle:Determination of saturation flow for all types of unopposed or opposed discharge. Traffic flow distribution between lanes in the same sub-approach.Identification of the critical conflict point for traffic streams that are served by different main signal phases (Min∑_1^n▒q/s).Signal timing for minimum total delay or other object function.Determination of traffic performance at normal and oversaturated conditions
Special consideration has been devoted to development of the following sub modules: Automatic calculation of inter-green times and minimum green periods which give instant feedback of geometry changes Short lane utilization and contribution to approach bottleneck capacity. Procedure for identification of the critical conflict point for complex intersection configurations and phase schemes including extra or alternative phases for efficient discharge of turning movements.Optimal signal timing including considerations to minimum green and lost time restraints Consideration of exit capacity Calculation of delay and other traffic performance variables for forcasted traffic flows including improved handling of oversaturation Linking of capacity model to existing modules for calculating impact on environment, costs and traffic safety.
The method is limited to isolated intersections, and based on fixed timed signals. Impacts of Traffic Actuated signal control is approximated by signal timing corrections (max green, green time extension intervals) based on traffic simulation results for different types of control strategies. In further work those corrections will be enhanced and also include the impacts of bus priority in vehicle actuated signal control using a more complex probability based model.