DHS traffic signal

With a new traffic controller programmed, city staff are now waiting on equipment to install what they believe will be a solution to traffic issues at the new lighted intersection at Pinion and Rock Road.

Questions persist about the new traffic signal outside Derby High School, at the intersection of Pinion and Rock Road, as it continues to be monitored in order to best optimize traffic flow.

Derby City Council members are curious, too, with Rocky Cornejo requesting an update on the time frame for the latest adjustments at the council’s Oct. 13 meeting.

“Even during no school, traffic will back up toward James [Street] already,” Cornejo said of the congestion at the new lighted intersection.

Following recent work on other traffic signals along Rock Road, equipment was identified and ordered to help implement a solution with the traffic signal in question. That equipment – new bi-modal signal heads that will allow a greater number of options for directing traffic – is expected to arrive in October and will help the city delineate peak and off peak operations for the new lighted intersection.

Split phasing was utilized at the Rock/Pinion intersection as a method to provide a protected left turn without a designated turn lane. In split phasing, only one direction of traffic is allowed through the intersection at a time.

Prompted by council member Nick Engle, Director of Planning and Engineering Dan Squires stated the reason a dedicated left turn lane wasn’t put in had to do with the time frame of the project, limited space (from James to Pinion) and limited usage, among other factors.

When plans for the new traffic signal were first set, Squires noted some changes didn’t get relayed from the traffic engineer hired by USD 260 to city staff, causing some initial issues. Additionally, city staff came to find out the traffic controller system at the new intersection would not split phase at one time and allow for non-split phasing at another time.

“I was really caught off guard,” Squires said.

The limitations of the traffic controller system have forced city staff to adapt, developing their own program to facilitate split phasing during peak hours (twice a day for 60 minutes each) and allow for non-split phasing at off peak times. 

City staff had to program a second controller with the ideal signal timings and Squires noted the final test will be installing that in a cabinet to make sure it functions as intended. That and the new signal heads (with flashing yellow turn arrows) will allow for “permissive” – or unprotected – left turns during off peak times.

Once the controller is tested in the cabinet, Squires said the new timing patterns can be transferred to the current controller to set both peak and off peak operations.

“We know this has been done before but do not know if it was done with the same equipment we utilize,” Squires said.

Not having the multimillion dollar traffic controller systems of big cities also makes it hard to tie two to three signals together (like the light at James Street) to better manage traffic flow, Squires pointed out, while the lack of side road demand the city is seeing is also uncommon when trying to have split phasing only at certain times.

Both Squires and Cornejo foresee the elimination of the protected left turn in off peak times helping with traffic flow, which Cornejo stated he is hoping to see in the next two to three weeks.

That depends upon when the new signal heads arrive, Squires said, but staff is hopeful that will be soon.

It was noted costs for the new software are anticipated to come in under $10,000, with Cornejo wondering if some of that could be shared by those in charge of the traffic study.

Mayor Randy White noted he is glad to have the option to complete a protected left turn at the new Pinion and Rock intersections, while Squires noted there have been some other positives – with the city gaining efficiencies in traffic along both James Street and Madison Avenue.

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