I-70 VARIABLE SPEED LIMIT

Clear Creek County, Colorado

The eastbound I-70 Mountain Corridor through Clear Creek County is a critical artery for recreational and freight traffic returning to the Front Range from the northern Colorado mountains and locations west. During congested conditions and inclement weather, there is a higher likelihood of traffic crashes that lead to the corridor traffic operations breaking down and can lead to more secondary crashes.

The I-70 Variable Speed Limit (VSL) project was initiated by CDOT to test, and if valid then implement, a theoretical solution that will reduce crashes during inclement weather and congested conditions. The theoretical algorithm, developed by the Muller team, takes inputs from measurements of road conditions using remote sensors and inputs from measurements of traffic flow rates to recommend a lower speed limit that is displayed on electronic signs. The project concept includes using the algorithm to automatically lower the speed limits using special software.

The project area is focused in the 12-mile eastbound Mountain Express Lane section of I-70, approximately from Empire through Idaho Springs. Muller led the Systems Engineering Analysis (SEA) process for the project, which is akin to planning and proving the system. The Muller team gathered the necessary data to validate the algorithm and develop use cases for further software development.

After the SEA process was completed successfully, and modeling showed that the system would be effective, we developed construction plans, specifications, and cost estimates for construction of the infrastructure to support the VSL system. The infrastructure to support the algorithm and software included additional traffic detectors, additional Road Weather Information System (RWIS) equipment including visibility sensors, and double-posted VSL signs every mile along the corridor.

OWNER

CDOT Region 1

SERVICES

Traffic Engineering & ITS

Statistics

26 Variable Speed Limit Signs | 11 Modified Overhead Sign Structures | 4 Weather Monitoring Systems | 3 Breakaway ITS Poles

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