Citywide Signal Retiming - On-Call TOITS Contract, Philadelphia, PA

Signal retiming has emerged as one of the most cost-effective methods to manage traffic, especially in cities like Philadelphia where widening streets is usually not an option. Urban assisted the City of Philadelphia (City) with retiming signals under an on-call contract. The City applied funds from a Delaware Valley Regional Planning Commission Signal Congestion Mitigation and Air Quality (CMAQ) grant to retime 270 signals along various corridors across Philadelphia.

Urban collected traffic and pedestrian data, including turning movement counts, GPS-based travel times, automatic traffic recorders (ATR), and field signal timings. We used Synchro 8 and SimTraffic to model conditions and designed optimized signal systems using a combination of Synchro/Sim Traffic and Thru Traffic. Urban also prepared work orders for each location.

App Combat

This program entailed a substantial data collection effort. To meet this challenge, We developed an iPad-based app to simplify the collection of field data at each location. We also created custom spreadsheets for the City to streamline the process of developing clearance calculation and pedestrian timings.  These spreadsheets also facilitated the QA/QC process. In addition, we hosted a “Best Practices” meeting with the City and other consultants to discuss the various techniques, and improve the retiming processes across all the projects. 

The modified signals allow enough time for vehicles to clear intersections and for pedestrians to cross streets. The retiming achieved benefit to cost ratios as high as 100:1. In addition, each intersection complies with Manual on Uniform Traffic Control Devices (MUTCD) timing requirements.