Office of Operations
photos of traffic merging onto congested highway, congestion in snowstorm, variable message sign, cargo, variable speed limit sign in a work zone, and a freeway at night
21st Century Operations Using 21st Century Technologies

Traffic Bottlenecks

Combating Bottlenecks


Using Proactive Rather than Reactive Signal Operations

Background: Traditional arterial signal systems use fixed timings, i.e., pre-set timings that rely on historical or "expected" traffic volumes. While the fixed timing programs can be different for A.M. or P.M. conditions, they nevertheless can't be interrupted except by manual override. Then it is necessary to manually return the timings to their original settings. Both of these tasks are time consuming and typically lag behind either of the actual needs.

Bottleneck Project: Traffic conditions along Highway 69 and Highway 323 are highly variable and had generated frequent citizen complaints over the years. Adaptive Signal Control (ASC) was installed on 16 intersections on these two highways, along with some minor geometric improvements and detection upgrades.

The Return: Traffic operations thereon have shifted from a reactive mode to a proactive mode dependent on information sent directly from the intersection detectors (volumes, wait times, et al) to the signal controllers. Highlights of the return on investment include reduced congestion and delay, fewer unnecessarily long stops, reduced fuel consumption (e.g., less idling) and an annual savings of close to $40,000 per year to the agency because signals need less human oversight, i.e., less retiming and attention.