DHS Rock Intersection

City staff continue to watch traffic patterns around the new lighted intersection at Pinion and Rock Road in order to optimize signal timing.

With the start of the school year, new experiences are to be expected. Traditionally those are going on inside the classroom, but students, parents and other residents are currently adjusting to something new outside of Derby High School – a lighted traffic stop installed over the summer at the intersection of Pinion and Rock Road.

Constructed as a way to improve traffic flow (including pedestrians) and school access, the new lighted intersection west of the high school will take some getting used to because of how it operates, which is unique compared to other signals in Derby.

“This signal is different than most signals in the fact that the whole intent of locating the signal at that location is to provide signalized access to the high school, but we don’t have a left turn lane at that location,” said Derby Director of Planning and Engineering Dan Squires. “So, to provide the protected left – that safe turn in – we have to do what’s called split-phasing. You completely hold the opposing flow of traffic while you allow those lefts because you don’t have a left turn lane.”

In short, northbound traffic will get a green light and arrow while southbound traffic is completely stopped at the Pinion and Rock intersection (and vice-versa). A dedicated left turn lane could be added later, but Squires noted it could not have been completed in the original time frame outlined for this new intersection. He also noted there are some challenges with that area that would make creation of such a lane more difficult than normal.

So far, city staff has gotten plenty of feedback on the new lighted intersection from the Derby community. Normally that is not the case, but Squires attributed that to two main factors –the high profile location of this intersection and its unique layout.

Preliminary timing (which has generated a bulk of the feedback) was based on a study around that intersection a year and a half ago. Changes since then have augmented traffic patterns along that stretch of Rock Road, which is something Squires said city staff couldn’t see until they started monitoring the real-time utilization of the intersection (which they are currently doing).

“A lot of things have changed since then. What we’re seeing, particularly in the afternoons, is that the amount of southbound traffic that we have on Rock Road is higher than it was a year and a half ago,” Squires said. “We didn’t have any way to test it until you’ve got real traffic using it. We don’t know that the traffic pattern has changed until we put the signal timing out there and we stand out there and watch it, and then they go back and start adjusting those timings. We’re adjusting it every couple of days to try to adjust for what we’re seeing real time.”

City staff will continue to monitor the new lighted intersection outside the high school to get the timing just right – watching peak traffic during school drop-off and pick-up, followed by off-peak times.

Squires noted the first day of school is traditionally a bad day to judge traffic patterns, but staff have been watching since and were even able to implement some changes to the timing of the intersection by the end of last week.

Residents’ concerns have been registered and Squires said staff continue to “work the bugs out.” They knew there would need to be some adjustments to the initial timing and they are now working out how best to do that.

“It’s just gonna take a little bit of time to get to where we’ve optimized it,” Squires said.