COMPARISON OF SOAP AND NETSIM: PRETIMED AND ACTUATED SIGNAL CONTROLS

Delay and fuel-consumption rates estimated by the relatively easy-to-use, deterministic Signal Operations Analysis Package (SOAP) were compared with results generated by the microscopic and stochastic Network Simulation Model (NETSIM). The study involved three cases of isolated signalized intersections: two-phase pretimed controller, two-phase fully actuated controller, and multiphase pretimed controller. More than 80 combinations of left-turning and through traffic volumes were investigated in each case. Whereas SOAP estimates excess fuel consumption at intersections, NETSIM generates total fuel consumption. The difference between the two was found to be fairly uniform and corresponded to a realistic 18-mile/gal fuel efficiency under uninterrupted 30-mph flow conditions. In terms of delay predictions, SOAP and NETSIM are found to be entirely compatible after the differences in delay definitions, SOAP's more conservative left-turn saturation-flow-rate relationship, and NETSIM's delay sensitivity to unit extensions for actuated signal controllers were taken into account. In addition, the volume/capacity ratio at which SOAP begins to overestimate delay due to the use of Webster's delay equation may be lower than now assumed. Last, the difference between SOAP and NETSIM average delays can probably be reduced by a more studied coordination between SOAP and NETSIM input parameters. Evidence is offered to the operating engineer that the easy-to-use SOAP produced results supported by the sophisticated NETSIM. (Author)