Douglas County Traffic Signal Modifications on Quebec Improve Traffic Flow

Success of project will lead to similar modifications in other areas

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Drivers traveling on Quebec Street from County Line to University will now experience fewer delays, fewer stops, save gas, and emit fewer pollutants thanks to traffic signal modifications completed by the Douglas County Traffic Division.

The Quebec Signal Optimization project involved: removing unnecessary left turn signals, removing a portion of some current medians to increase driver visibility for left turns, modifications to signage and creating a by-pass median at University and Quebec by the post office. Adding a by-pass median allows those going west on University to by-pass the traffic signal, while those heading east on University will continue to stop for vehicles exiting the post office.

A before and after analysis determined that in just one hour during both the morning and evening rush hours a total from all cars traveling during this time period saves 198 hours of time; eliminates 4,979 stops; saves 225 gallons of gas; eliminates 15.73 kilograms of carbon monoxide and 3.06 kilograms of nitrous oxide.

In an effort to determine if tax money was well spent, Douglas County calculated a cost/benefit ratio for this project. The total cost for the project was $200,074 and the total benefit or savings (using a total of all travelers) for one year is calculated at $805,750 resulting in a cost/benefit ratio of 4.04. Any ratio above one is considered worthwhile. The high cost/benefit numbers are not unusual with traffic signal modification and retiming projects, as they tend to have a low relative cost with significant impacts on congestion.

This Quebec signal synchronization project is a direct result of Douglas County’s 2008 Citizen Survey and the Highlands Ranch Transportation Improvement Program (HRTIP). The 2008 Citizen Survey revealed that 96 percent of Douglas County residents felt that improving traffic flow by synchronizing lights was a medium to high priority. The HRTIP also recognized that traffic signal improvements were a high priority for citizens therefore recommending improvements be completed in the next one to three years (the HRTIP results were finalized in January 2007). The Quebec Street Corridor was specifically identified as one of the areas needing improvements in the HRTIP.

The success of this project has led the Douglas County Traffic Division to make similar modifications on Highlands Ranch Parkway from University west to Deer Creek and on University from Quebec to Dad Clark. Work will begin in mid-October and is estimated for completion approximately 45 days later. Citizens will experience minimal disruption during this time. Douglas County staff is also working with the Denver Regional Council of Governments (DRCOG) and the City of Lone Tree on a retiming project on County Line from Quebec to I-25.