Give me the green light: Sandy works on syncing traffic lights
May 11, 2020 12:50PM
By Justin Adams
By Justin Adams | [email protected]
If you’ve noticed that you’re spending a little less time at red lights this spring, you can thank Sandy City.
This fall the city contracted with Avenue Consultants, as well as the state and county, to conduct a study of the city’s traffic lights and subsequently resynched them in an attempt to get Sandy residents and visitors moving a little more smoothly through the city.
The study focused on nine “signal corridors,” streets that handle the most traffic throughout the city, such as State Street, 10600 South, 9000 South, 700 East and 1300 East. The goal of the project is to make sure that all the signals along those streets are in sync with one another.
Britney Ward, the city’s transportation engineer, explained the strategy behind signal corridors during a report to the city council on April 14.
“Typically in a signal corridor we would set all the cycle lengths to be the same, and then we would offset the times by a few seconds or depending on how close together those signals are spaced so they are coordinated,” Ward said.
If done correctly, the strategy results in more coordinated and continuous flows of traffic throughout the city.
Councilwoman Marci Houseman summarized it like this. “Though there may be a longer delay when encountering a red light, it seems that overall we are going to have residents encountering green more often. That was the goal, to have a continuous flow,” she said.
Different cycle lengths were also applied to the same area for different parts of the day. For example, on State Street between 9000 South and 10600 South, traffic signals are set to a 100 second cycle in the morning. But during the evening commute hours when people head home in more concentrated numbers in a smaller window of time, they change to be 150 second cycles. (A cycle length is defined as the time needed to serve all signal phases.)
To determine what configuration would work best for each traffic signal, the city and its partners used a microsimulation engineering program called Synchro. Using the program, they were able to test multiple options for each intersection.
The program also allows the city to estimate how much time and money will be saved by Sandy residents as a result of the changes. It is expected that daily travel time throughout the city has been decreased by 1,008 hours, which translates to 71,000 gallons of gas saved per year.
While this is the first time Sandy City has done a traffic signal synchronization study in 10 years, Ward said that they plan to begin doing them every five years so as to stay ahead of changes to traffic patterns caused by new development.