Illinois DOT Signal Coordination and Timing

Districts 6, 7, 8 and 9, Illinois

The Illinois Department of Transportation (IDOT) hired SRF to complete signal coordination and timing efforts on multiple highways in Districts 6, 7, 8 and 9, which included the following routes:

  • IL 32/33 in Effingham (District 7): six signals
  • IL 157 in Cahokia (District 8): 10 signals
  • IL 3 in Columbia (District 8): five signals
  • West Highway 50 in O’Fallon (District 8): seven signals
  • IL 13 and US 51 in Carbondale (District 9): 23 signals

To initiate each project, SRF held in-person discussions with IDOT District Engineers to set project goals and determine preferences for each District, which helped minimize IDOT review efforts. Each project involved traffic and base data collection, base model calibration for verification of undesirable conditions, proposed time-of-day model and plan creation, recommendations for phasing and equipment improvements, implementation, and final documentation.

Other highlights of our work include:

  • SRF determined unusual pedestrian overlap phase conflicts on the IL 32/33 corridor in Effingham and recommended a revised phasing plan to the District 7 project manager who facilitated the change prior to implementation.
  • The IL 3 corridor in Columbia experienced high profile crashes prior to the SCAT study, and SRF reviewed safety in addition to the SCAT initiative. We completed a thorough safety review of the corridor that included field standards review, crash report investigation, geometric and operational contributors to the evident crash patterns, and investigation of potential improvement alternatives through Highway Safety Manual methodologies, including using the Interactive Highway Safety Design Model and economic appraisal techniques.