GHA was selected by IDOT to optimize the signals on Touhy Avenue. The bridge for Harts Road over the North Branch of the Chicago River was reconstructed and as part of this construction project, the adjacent system of signalized intersections along Touhy Ave was optimized. This corridor had not been optimized in over a decade and was not efficiently handling current traffic volumes and patterns.

After performing turning movement counts at each intersection, GHA staff created Synchro models for the corridor. Using these models, GHA engineered new traffic signal programming to improve traffic flow, efficiency, and safety. GHA staff then implemented these new signal timings in the field, observing how traffic operated. Along with IDOT staff, GHA adjusted signal timings at the intersections to further improve traffic operations.

One bottleneck for this system was the railroad crossing at Touhy Ave and Lehigh Ave. Many commuter trains pass through during rush hour, backing traffic up repeatedly. GHA adjusted the way that the traffic signal recovers from railroad preemptions, allowing the queue of vehicles to clear after each time the gates are down. This prevents long delays caused by multiple consecutive trains.

As a final review of the new timings, GHA staff drove the corridor in all applicable time periods, recording speed and acceleration via GPS tracking. By comparing this data before and after implementation, GHA staff estimated overall improvements to driver delay, average stops, and vehicle emissions. This information is included in a final report that was submitted to IDOT.
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