After the UPCC contacted the City about the possible installation of protected left-turn signal for northbound Colorado traffic turning west onto Iliff, a traffic study was conducted by the City. Here are the City’s findings:
The following report is from David DiGiacomo, a Staff Engineer, Traffic Engineering Services for the City and County of Denver:
I observed the northbound left turns on Wednesday, February 16, 2011 from 7:30 – 8:30 am and 4:00 – 6:00 pm. During the morning time period for the northbound left turn, there were 93 vehicles waiting for a green indication, 88 vehicles making a left turn, and five vehicles that were held over and did not make it through the first cycle. During the evening time period for the northbound left turn, there were 172 vehicles waiting for a green indication, 146 vehicles making a left turn, and 26 vehicles that were held over and did not make it through the first cycle. In order to meet the warrant for a left turn arrow, 54 vehicles would need to be held over in a one hour period or 108 vehicles in a two hour period. This northbound left turn falls short of that volume during both the morning and evening peak hours.
A warrant based on accidents requires at least 5 correctable approach turn accidents in a 12 month period for the last three years. For the northbound left turn, there was one correctable accident reported within the last three years. Therefore, the accident warrant is not met.
We appreciate you bringing this intersection to our attention. However, a northbound left turn signal modification for this intersection is not warranted at this time. If you have any questions or need further information, you can contact me at 720-865-3166.