Are traffic lights timed? KSAT Explains

Local traffic signals are controlled and maintained by three entities, though they sometimes merge

No matter where you’re from or where you’re going, every driver deals with traffic lights. And perhaps the biggest complaint? “They’re not timed well.” Or worse yet, “they’re not timed at all.”

Those are gripes local public works departments hear often.

“Yes, yes we do,” said Tony Vasquez, Bexar County Public Works Division Chief. “Mostly that people are at the light too long or it didn’t let enough cars go through.”

It’s much the same within the City of San Antonio.

“We get a lot of calls for folks that are saying that they’re waiting too long for a traffic light to turn green or something like that the time that the light is green isn’t long enough,” said Marc Jacobsen,” said Marc Jacobson, Transportation Systems Management and Operations Program Manager for the City of San Antonio Public Works Department.

Yup, the lights are timed

Three groups are in charge of controlling, timing, and maintaining local traffic signals: the city, the county, and the Texas Department of Transportation, or TXDOT.

“I think that there’s two common misconceptions. One is that you know, these signals are not timed correctly. Well, they are,” said Dale Picha, TXDOT Director of Transportation Operations, San Antonio District.

“The other is who’s responsible for that signal,” he added.

The Texas Administrative Code says that local governments own and maintain the traffic signals in cities that have more than 50,000 people.

In our region, that applies to San Antonio and New Braunfels.

Outside of those, TXDOT owns roughly 200 traffic signals on local frontage roads, but the state agency pays the City of San Antonio to maintain about 130 of those lights.

In cities within Bexar County that have fewer than 50,000 people, TXDOT owns and maintains those lights.

However, there are exceptions where streets in those smaller municipalities are connected to San Antonio streets.

Take Leon Valley, for example.

“We pay the City of San Antonio to maintain those traffic signals for us in Leon Valley just because San Antonio has signals north of there and they have signals south of there,” Picha said. “So it kind of ties it all together as one system.”

Lights, Camera, Action

Three factors determine when traffic lights go from green to yellow to red:

  • Pre-programmed timing schedules
  • Motion sensors
  • Time of day

The City of San Antonio lights usually have timing programs for morning rush hour, evening rush hour, and the times in between.

“For some locations, we have even more than that because we have some locations that have like a heavy lunch period, for example,” said Jacobson. “Or some that have unique traffic patterns on the weekend. And so we may have a different timing plan that runs on Saturday versus one that comes on Sunday.”

Jacobsen adds that the more cars there are lined up at a red light, the more time they will be given to travel when it turns green.

But that doesn’t mean a light will stay green long enough for every car to make it through. Side streets and left turn lanes have to go some time.

The city reevaluates the timing of the 1,145 lights it operates every three to five years or if there is a new development that might change traffic flow, like a subdivision or shopping center.

Jacobson says City Public Works crews will also re-examine a light if they get complaints through the city’s 311 call system.

Bexar County Public Works is in charge of far fewer lights: 62 to be exact.

However, that number is growing and includes a new light at Wiseman Boulevard and Tillman Ridge to accommodate a new subdivision.

“There’s always going to be a minimum time and a maximum time, which if there’s no traffic, it’ll just do the minimum time,” said Vasquez. “If you do have traffic, you know, there’s a lot of cars, it’ll shut off at the maximum time and allow them the most cars it can while still keeping in mind that there’s another leg that needs to go through.”

Times and Traffic

That minimum and maximum time varies at every intersection, according to Vasquez.

The city says lights will “typically” be green for 60 seconds on a main street, 30 seconds for a smaller street, and 15 seconds for left turn lanes.

City of San Antonio Public Works lists the most traveled intersections in San Antonio as:

  • SW Military Drive at Zarzamora Street
  • Culebra Road at Westwood Loop
  • Potranco Road at Hunt Lane

Bexar County Public Works says it doesn’t track an average time for green lights, but they do know the busiest intersections in the county:

  • Alamo Ranch at Lone Star Parkway
  • Alamo Ranch at Alamo Ranch Parkway
  • Bulverde Road at TPC Parkway

About the Authors:

Myra Arthur is passionate about San Antonio and sharing its stories. She graduated high school in the Alamo City and always wanted to anchor and report in her hometown. Myra anchors KSAT News at 6:00 p.m. and hosts and reports for the streaming show, KSAT Explains. She joined KSAT in 2012 after anchoring and reporting in Waco and Corpus Christi.