Installation of adaptive signal control systems on two corridors in Colorado improved travel times by 9 to 19 percent, increased average speed by 7 to 22 percent and maintained or improved level of service at the studied intersections.

Colorado DOT's comparison of two adaptive signal deployments.

July 2012
Greeley,Colorado,United States; Woodland Park,Colorado,United States

Summary Information

The Colorado Department of Transportation (CDOT) implemented two separate adaptive signal control systems, one in Region 2 and another in Region 4. This study was done as a comparison between two different technologies deployed in two different environments. In Region 2, the City of Greeley, in conjunction with CDOT installed InSync adaptive signals at 11 10th Street (US 34 Business) intersections. In Region 4, QuicTrac adaptive signals were installed at 8 intersections along US 24 in Woodland Park. These upgrades were made to meet the goals of the FHWA "Every Day Counts" initiative.

On the 10th Street and US 24 corridors, weekday travel times improved by 9 and 6 percent, respectively. Also on weekdays, average speed increased by 11 and 7 percent, respectively. These improvements in travel time and average speed are largely due to the decreases in stop delay and number of stops. The number of weekday stops decreased by 37 percent on the 10th Street corridor, with 13 percent less stop delay and by 8 percent on the US 24 corridor, with 15 percent less stop delay. The trend was similar, but of larger magnitude on weekends. (See Tables 3 and 6 in the source report for more detail.)

Additionally, the level of service (LOS), as calculated by the definitions in the latest Highway Capacity Manual, at each of the 8 total intersections examined for the two corridors showed that the adaptive signal control was operating the intersections at either the same level of service or better. (See Table 5 in the source report for more detail.)


The weekend traffic on the US 24 corridor was nearly 30 percent lower in the after study due to seasonal travel patterns and may affect the weekend results reported.

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Adaptive Signal Timing Comparison between the InSync and QuicTrac Adaptive Signal Systems Installed in Colorado

Published By: Colorado Department of Transportation

Source Date: July 2012



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Goal Areas



traffic signals, adaptive signals, adaptive signal control

Benefit ID: 2012-00809