Development Type: None
Services Provided: Traffic Signal Tune-Up
Client: City of Woodbury
Two years ago, we launched our Traffic Signal Tune-Up service. Why a Tune-Up? Well, just like a car, traffic signals need periodic reviews to keep them running smoothly. Our service examines the operations, ensuring the current standards are met and the timing reflects the traffic patterns, and the infrastructure, testing push buttons and detectors, etc. As far as we know, our service is the first to pair the traffic signal re-timing with basic maintenance.
Coincidentally, we are also entering our third year helping the City of Woodbury, Minnesota examine their signals. At the end of this year, we will have completed reviewing all the local signal systems for the City. Here are a few take-aways we have learned from our work the City’s systems:
Don’t Assume the Timing is Current. As we worked with the City on which signals to review and the order, three or four signals were not on the list. These systems had been relatively recently updated with flashing yellow arrow operation and, it was assumed, with proper timing to take advantage of the new arrows. Upon closer review and a little digging into that prior project, a standard set of parameters had been entered to make use of the flashing yellow arrows. These parameters did not represent an update, but more of a place-holder. The intersections were put back on the list to ensure the timings were reflective of the new equipment and the most up-to-date travel patterns.
Group Adjacent Intersections. Although these intersections all operated independently, the movements at one influenced the movements at another. While that is pretty obvious (especially to drivers), that means it may make more sense to update all signals in a general area rather than chronologically by date of last revision.
Coordinate with Other Agencies. Another obvious one that goes along with paying attention to surrounding signal systems. In this case, the County operates adjacent signals that were linked, but not coordinated together. Through discussions with the County, we were better able to account for those adjacent operations as well as obtain another perspective on how the City’s study intersections were operating. Thanks to the County for their help, which are making our revisions that much better.
48-Hour Counts Make a Difference. Our standard Traffic Impact Study process and data collection default is a 48-hour count. We are slowly trying to convince the rest of the industry to follow our lead. The benefits for this project included being able to better see the length of different peak periods and notice peaks that extended into the evening in the retail areas. Most interesting was reviewing the subtle shifts in traffic, in terms of time of day, between the two daily counts. The average of the two days smoothed those small shifts, allowing our revised signal timing to better accommodate the natural variations in traffic flow.
A Few Seconds Really Do Matter. In some cases, we aren’t shifting significant amounts of time. We update the yellow and red times, re-calculate the pedestrian crossing times, and make a few adjustments to the green times. But those few seconds seem to be significant, both to the driver and to our review of operations. The City even received at least one call from a resident happily noting the change.
The benefits of updating traffic signal timing are well known. The Institute of Transportation Engineers (ITE) says it best – “Traffic signal retiming is one of the most cost-effective ways to improve traffic movement and make our streets safer.” We agree and are grateful to be helping the City of Woodbury improve their streets. Download our Traffic Signal Tune-Up price list to see how we can help you.