Traffic coming in-and-out of La Jolla: Early data on Adaptive Signal Timing shows traffic snarls eased


When the pilot program for automated Adaptive Signal Timing was tested on Lusk Boulevard in the Mira Mesa area, the change in traffic was dramatic. Soon after the system was installed, it caused an 18 to 24 percent reduction in traffic congestion, depending on the time of day. To see what the system could do for other heavily-trafficked thoroughfares, the City of San Diego installed the system (also known as Traffic Light Synchronization) on La Jolla Parkway in early June.

Once installed, city traffic engineers, chiefly Duncan Hughes, said they would review the efficiency of the system after three months. With early data rolling in for the La Jolla project, though engineers find the adaptive signal timing to be successful, the actual decrease in traffic congestion has been tepid. (When presented as a La Jolla Light poll question, only 55 percent of respondents said the system was helping to ease traffic entering/exiting the Village of La Jolla.)

“The system on Lusk Boulevard has shown a bigger change than what we’re seeing on La Jolla Parkway,” Hughes explained. “But the La Jolla project has provided us with good information. This area, as we knew, is heavily congested. I think the system has been able to reduce the travel time and number of vehicle stops. From that standpoint, it has been a success. We’ve heard reports of increased delays on the side streets, but we wanted to handle the traffic on La Jolla Parkway and Torrey Pines Road.”

Using cameras mounted on the mast arms over the intersections of La Jolla Parkway at Torrey Pines Road, at La Jolla Shores Drive, and at Ardath Lane, Adaptive Signal Timing makes use of the camera images to adjust green light duration based on real-time increases and decreases in traffic.

Before the system was installed, a typical green light duration was 170 seconds, regardless of traffic volumes. With the new system, green light durations vary between 140 to 190 seconds. The system resumes to “un-adapted” from 10 p.m. to 6 a.m., when it maintains consistent timing.

Hughes said the data gathered over the last three months includes the number of cars on La Jolla Parkway in both directions in 15-minute increments and peak times. “Traffic gets very busy after 6 a.m., then there is a tiny lull, and then it gets busy again. Peak times for traffic counts include 8:15 a.m., 1:30 and 5:15 p.m.” With that data, the engineering firm that installed the system enginners who installed the system set the signals, “which are now talking to themselves and adapting automatically,” Hughes said. He added that around 7:15 a.m. most weekdays, 879 vehicles are on La Jolla Parkway entering The Village. During those times, green light durations are their longest.

Apps data helps, too

The city is also using data collected through the GPS mapping app Waze, which can display the speeds cars are going, and when and where there are traffic jams. “The City of San Diego has a partnership with Waze that allows us to look at traffic patterns,” Hughes said.

With the data, city engineers can compare traffic flows seasonally, as school years come and go, and around holidays.

“If we need to adjust the cycle ranges or dismiss them altogether in the winter, we can do that. Or, using the Waze data, we can change the flows if we see something out of the ordinary,” he said. “I think we’re on the right path with this system. I don’t think we’re seeing the dramatic traffic savings we saw on Lusk. But we are going to continue with other areas and to monitor traffic flows on La Jolla Parkway.”

To do so, Hughes said the city will appoint someone to monitor the data, adjust the system as needed, and “have more eyes on this” as more Traffic Light Synchronization systems are installed.

The next areas to get the system are on Mira Mesa Boulevard and Rosecrans Street, spanning the Midway and Point Loma areas. Installation of the camera equipment has already begun on Rosecrans Street.

A trade-off with this system, one that has been reported to the city and to the Light, is the backup of traffic on side streets or streets with lighted intersections that feed into La Jolla Parkway or Torrey Pines Road.

“It was a little bit of a pick-your-poison scenario,” Hughes said. “This system has helped get traffic moving on the parkway and that is what we determined was needed. (Delays on side streets were) something that was a concern initially, so we asked the vendors who set up the system to balance out the delays a bit, and they did that to a certain extent.”

City Council President and La Jolla Shores resident Sherri Lightner has advocated for the installation of this system throughout her time on the city council. When she sat down with the Light in January, she listed Traffic Light Synchronization as a priority. “I’m very pleased so far with the signal synchronization on La Jolla Parkway. The number of traffic complaints our office has received has decreased dramatically since the installation. I’d also like to see signal synchronization systems continuing through the Village and also around UCSD.”