Field tests were conducted in four cities (Reston, VA, Chicago, IL, Seattle, WA, and Tucson, AZ) to study and apply traffic control systems that operate in real time, adjusting signal timing to accommodate changing traffic patterns. This type of traffic control is known as adaptive signal control. Adaptive signal control software uses detection to interpret traffic approaching a traffic signal, and using mathematical and predictive algorithms, adapts the signal timings accordingly to optimize the performance.
The methodology for the evaluation included laboratory simulations and field tests. The laboratory simulation testing demonstrated that adaptive control algorithms can decrease travel time and improve traffic volumes. Field tests in the four cities supported the simulation testing results.
Simulation results demonstrated that compared to optimized traffic signal timing plans, adaptive control algorithms can decrease travel time and improve traffic volume handling by approximately 3-7 percent.
Field tests performed in Virginia (OPAC) and Washington (RHODES) during high directional flows showed that travel times improved by approximately five percent, verifying simulation results.
In Illinois, the RTACL system dramatically improved travel times by 12-53 percent and decreased delay up to 100 percent along certain corridors within the network.