A traffic-light synchronization project along the University Avenue commute corridor in Palo Alto and East Palo Alto is speeding up traffic on average by 28% and decreasing travel time by 13% for all of the peak travel periods, according to a consultant's report submitted to the Metropolitan Transportation Commission.
The report measured the results of synchronizing 19 signals starting last May along the corridor from Middlefield Road to the Dumbarton Bridge during the weekday peak traffic flow and midday on weekends.
Palo Alto, East Palo Alto and Caltrans applied for a grant from the Metropolitan Transportation Commission Program for Arterial System Synchronization in July 2018. The $126,275 project was designed to improve often horrendous commute conditions along the arterial roadway. The June 19 final project report with a benefit/cost analysis was created by transportation planning consultants TJKM.
An average of 24,000 to 33,400 vehicles use this section of University Avenue during weekdays, according to the report. Donohoe Street in East Palo Alto, which funnels traffic from Embarcadero Road to northbound U.S. Highway 101 and to University Avenue to the Dumbarton Bridge, has an average of 10,000 to 25,400 vehicles during weekdays.
The commute corridor was not only slow but also unsafe in certain places. Five intersections also exceeded the statewide average collision rate prior to the synchronization along University Avenue: Lincoln Avenue, Chaucer Street, Guinda Street and Middlefield Road in Palo Alto and Woodland and Scofield avenues in East Palo Alto. The signals now have updated green, yellow and red light minimum times so that traffic can clear the intersections. Insufficient yellow-light timing can sometimes cause rear-end collisions and inadequate red-light timing can cause right-angle crashes, according to the report.
The study looked at morning, midday, 1 p.m. and 2 p.m. afternoon commutes during the school year and midday weekend traffic.
"University Avenue showed significant decrease in stop delay, travel time and increase in speed during the weekday a.m., midday and p.m. ... and weekend midday peak periods for northbound and southbound directions," the study noted. There was an approximately 25% reduction in stop delay, a 21% reduction in stops per vehicle and a 13% decrease in travel time with a 28% increase in speed for all of the peak periods since synchronization.
Studies before and after the synchronization measured intersection improvements and "floating" car runs. The latter covered a vehicle's one-way trip of the entire length of a study corridor. The study captured travel time, speed, stopping time, number of stops and other delays.
"Before" data along a 2.31-mile stretch of University Avenue between O'Brien Drive in East Palo Alto and Guinda Street in Palo Alto found that during afternoon commutes at 2 p.m., drivers heading north experienced an average stop delay of 67 minutes and 5 seconds. Total travel time was 70 minutes and 55 seconds with an average speed of 3 mph.
An "after" study found the same corridor at 2 p.m. had a stop-delay average of 13 minutes and 38 seconds and a travel time of 18 minutes and 43 seconds. Average speed increased to 8 mph.
Southbound commutes along the same stretch also improved. Vehicles had total stop delays of 4 minutes and 44 seconds at 2 p.m. before the synchronization, which improved to 52 seconds after the changes. A total travel time of 10 minutes and 6 seconds before synchronization changed to 6 minutes and 12 seconds. Speed rose from 14 mph to 22 mph, the study showed.
The study also looked at synchronization along a 0.31-mile stretch of a problematic intersection in East Palo Alto, at Donohoe Street between University Avenue and the Ravenswood Shopping Center. Donohoe Street showed an average 64% reduction in stop delay, 50% reduction in the number of stops per vehicle and a 56% reduction in travel time. Speed increased 120% for all peak periods, the consultants found.
Westbound traffic at 1 p.m. was Donohoe's busiest time, with stop delays of 6 minutes and 7 seconds and an average speed of 3 mph. After synchronization, motorists experienced stop delays of 2 minutes and 11 seconds and traveled at an average 11 mph.
The synchronization program has benefits for pedestrians at crosswalks. "Walk" and "Don't Walk" clearance timing was updated to allow pedestrians to safely cut through intersections based on the state's transportation standard of a current walking speed of 3.5 feet per second.
The report also looked at the average savings in dollars over a five-year period, which is considered the project's "lifetime." The project is estimated to have a travel-time savings of approximately $45,187,857 (calculated as 50% of the wage rate for off-the-clock travel or $20.09 in 2014) and $2,455,618 in fuel-consumption savings. The synchronization also will reduce the amount of carbon dioxide emitted by vehicles by 13.2 tons.