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Illinois’ First Adaptive Traffic Signal System – Aptakisic Road

October 27th, 2015

Lake County Division of Transportation.

The Lake County Division of Transportation (LCDOT) recently completed the installation and validation testing of the first Adaptive Traffic Signal Control system in the State of Illinois. This type of traffic signal control is unique because unlike the traditional closed loop signal systems, the adaptive system continuously makes dynamic signal timing changes in response to active traffic conditions. Based on the traffic volume traveling on the adaptive corridor and the vehicle spacing, the adaptive equipment determines the optimal cycle length, ideal green time and can even skip signal phases.  Adaptive traffic signal control also has a distinct advantage in being able to better manage traffic incidents and special events.  The flexibility to react instantaneously to roadway conditions, results in lower vehicle delay while increasing traffic flow.

LCDOT was encouraged by the Federal Highway Administration (FHWA) to identify possible corridors that would be candidates for adaptive signal timing after FHWA’s acceptance of Adaptive Traffic Signal Control systems for Federal Projects. LCDOT ultimately selected the Aptakisic Road corridor between Parkway Drive and Brandywyn Lane as the first candidate location for the implementation of an adaptive traffic signal control system. The corridor contains eight signalized intersections, including a railroad interconnected signal.  There are diverse land uses within the corridor ranging from retail to office space to single-family homes.  A primary reason for selecting Aptakisic Road was to take advantage of the substantial traffic signal infrastructure that the County had already installed along the corridor and to integrate the new adaptive traffic signal control system into LCDOT’s PASSAGE system.

CBBEL worked closely with LCDOT and Jon Nelson, Engineer of Traffic to develop and prepare the Congestion Mitigation and Air Quality (CMAQ) application for the adaptive traffic signal control demonstration project. As part of the application process, CBBEL developed detailed cost estimates and system evaluation parameters to meet FHWA standards for a demonstration project. The project subsequently received approval for federal funding for Phase III Construction and Construction Engineering.  LCDOT decided to fund the Phase I and Phase II engineering to expedite the overall project schedule. Subsequently CBBEL performed all Phase I and Phase II engineering related services while LCDOT developed the Systems Engineering Report for the adaptive traffic signal control system.

CBBEL coordinated the Phase I environmental documentation and processing through LCDOT and developed detailed engineering plans and specifications for the proposed adaptive traffic signal control system. This consisted of a detailed field reconnaissance for each intersection to evaluate equipment upgrades and detection requirements.  This also included evaluating the existing cabinet space available to accommodate the adaptive equipment and ultimately resulted in determining that five of the existing traffic signal cabinets would need to be replaced.



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One of the design challenges was coordinating the County’s video detection equipment and adaptive equipment to operate simultaneously so that intersections could still be able to communicate with the County’s PASSAGE system with the adaptive system activated. The project also involved the incorporation of additional video detection cameras specific to the adaptive traffic signal control system.  Additional detection included in the project consisted of Bluetooth detectors that independently calculated the roadway’s travel time which was used in the Validation Study.

CBBEL also developed the system’s Validation Study specification that established the requirements that the contractor needed to follow to evaluate the traffic signal performance in both the before and after condition, which was a key component of satisfying the Systems Engineering Analysis. The project was locally let in December of 2013 and the system has been running the adaptive programming with some restrictions in place since late 2014.  With the adaptive programming active, the County reports that the corridor can carry as much as 40% more vehicles in the AM peak period and 15% more in the PM peak period when comparing the same travel time to an optimized time-of-day interconnect system.

G. Michael Ziegler, PE, PTOE
Vice President
Head, Traffic Operations Department