Traffic Signal Retiming in Bloomington, Indiana

As part of this citywide signal retiming project, American Structurepoint developed traffic signal timing information for 84 traffic signals (68 within coordinated signal systems and 16 isolated intersections). New timings were developed and implemented along eight coordinated systems throughout the city, which required cross-coordination at multiple locations along each corridor.

American Structurepoint conducted a field inventory for all of the study intersections to determine existing conditions and develop a comprehensive list of the corridors to be retimed. The City's Aries zone manager software was used to upload the existing controller databases at the locations where possible, while the remaining databases were uploaded in the field.

Based upon the information from the field inventory, seven-day machine tube counts were collected along each corridor, with the locations determined based upon the number of intersections per corridor. This information was analyzed to determine the proposed corridor pattern operating times. Turning movement counts were collected during this same time period to ensure accuracy of the data and eliminate delays due to processing times.

Basic controller timings were developed for all coordinated and uncoordinated signals to ensure they were in compliance with the current requirements. Special attention was paid to the pedestrian timings, yellow change, and all-red intervals to ensure they were meeting (or exceeding) the recommended times. During this step, intersection operations were evaluated to determine whether alternate phasing or changes to pedestrian operations were recommended, and results were reported to the City.

During the initial phase, it was determined that two of the City's primary corridors were operating in free mode during the overnight period without any actuation or coordination, causing unnecessary delay. At this point, it was determined that the unusual step of providing 24-hour coordination would be incorporated to eliminate unnecessary stops along these corridors. The City's primary goal for this study was to reduce vehicle progression speed while optimizing travel throughout, which was achieved through innovative signal timing methods. Additionally, creative programming methods were used to reduce the impacts of the high school release on the surrounding roadway network while reducing the amount of time it takes to clear the school buses and exiting student traffic.