Traffic Signal Coordination & Timing – Illinois DOT Districts 6–9

The Illinois Department of Transportation (IDOT) retained SRF to improve signal coordination and timing across multiple high-traffic corridors in Districts 6, 7, 8, and 9. The goal was to enhance traffic flow, reduce congestion, and address corridor-specific safety concerns through refined traffic signal operations.

Corridors included:

• IL 32/33 in Effingham (6 signals – District 7)
• IL 157 in Cahokia (10 signals – District 8)
• IL 3 in Columbia (5 signals – District 8)
• West Highway 50 in O’Fallon (7 signals – District 8)
• IL 13 & US 51 in Carbondale (23 signals – District 9)

Each project began with a collaborative kickoff meeting between SRF’s project team and IDOT district engineers to define goals, minimize review cycles, and tailor strategies to each corridor’s unique operational challenges.

Project Deliverables & Methodology

• Collection of traffic volumes, turning movement counts, and signal infrastructure data
• Base model calibration to identify current deficiencies
• Development of optimized time-of-day signal timing plans
• Phasing improvements and controller equipment recommendations
• Field implementation and post-deployment validation
• Final documentation aligned with IDOT standards

Targeted Corridor Improvements

• In Effingham, SRF discovered pedestrian phase conflicts on IL 32/33 and proposed a revised signal phasing plan. IDOT District 7 approved the updates prior to final implementation.
• In Columbia, IDOT requested a corridor safety review in response to recent high-profile crashes. SRF expanded its scope to include crash analysis, operational review, and Highway Safety Manual methodologies, using the Interactive Highway Safety Design Model (IHSDM) and economic appraisal tools to evaluate improvement alternatives.

These efforts not only improved traffic flow and reduced travel time but also provided targeted safety enhancements that support long-term system performance and reliability.

Resource Links
Illinois Department of Transportation (IDOT)
Highway Safety Manual – AASHTO
Interactive Highway Safety Design Model (IHSDM)

Internal Categories:
Traffic and Technology

More from:
Illinois