Assessment of the Benefits from Signal Hardware Improvements

Signal equipment upgrades (e.g., multiple timing plan capability and/or signal interconnection) are commonly used to improve the quality of traffic flow in urban arterials and networks.  These signal control improvements generally result in considerable delay, stops and fuel savings but the benefits vary widely on different networks.  Procedures are needed to provide guidance on the benefits likely to be achieved from improving signal hardware.  This report discusses the major factors that influence signal equipment performance and presents the findings of the assessment of the impacts from alternative control scenarios to assist practising engineers in conducting analyses of proposed equipment upgrades.  The effectiveness of hardware improvements was assessed against the optimal timings with the available equipment, in order to differentiate benefits from installing hardware from benefits from signal retiming.  Alternative signal operations strategies were simulated through the NETSIM model on eight real-life test networks representing a wide-cross section of traffic and geometric characteristics. Optimized timings for each control mode were developed using the TRANSYT, PASSER and SOAP optimization models.  In addition, field measured improvements in traffic performance from three demonstration projects were analyzed and compared with the simulation results.  The results from the study showed the significance of the geometric and traffic characteristics on the impacts of hardware improvements and identified trade-offs between alternative strategies.  A set of procedures was developed to assist practicing engineers in determining the need and the benefits likely from upgrading the signal equipment.