Sonoma County motorists merging onto the freeway have zipped past idle metering lights for more than a decade without noticing. But when transportation officials switch them on next year, the on-ramp traffic signals will give many drivers pause.
Caltrans began installing metering lights in 2001 as part of the Highway 101 widening project. Earlier this year, the Metropolitan Transportation Commission mandated that metering lights be activated. The regional transportation body could suspend discretionary funding for noncompliance.
Officials say the lights, which allow cars onto the freeway at preset intervals, will help with traffic flow.
"The global reason why this is necessary is to use technology to get the best performance from our infrastructure," said James Cameron, deputy director for projects at the Sonoma County Transportation Authority.
Metering lights are already used on other Bay Area freeways and have drastically reduced congestion, Cameron said. The signals reduced travel time by 19 minutes on a 10-mile stretch of Highway 101 in San Mateo County. On Highway 85 in San Jose, travel time was reduced by 52 percent.
Lights were installed at most on-ramps from Windsor to Petaluma as crews added carpool lanes through Sonoma County. The widened on-ramps also have carpool lanes, which could be incorporated into the metering light rollout.
Officials will switch on the lights as early as March, Cameron said. Until then, staff have been studying traffic patterns to determine the timing of the meters and the hours of operation. The meters could be used during carpool hours, Cameron said.
One of the biggest concerns is making sure on-ramp traffic does not back up onto city streets, Cameron said. Sensors under the road will detect when traffic is piling up and will trigger a green light if the queue gets too long.
"It will not back up onto local streets," Cameron said.
Lighter highway traffic would be a huge relief to travelers, especially in the more densely populated area of the county from Santa Rosa south, said Rob Sprinkle, Santa Rosa traffic engineer. But drivers will need to get accustomed to stopping at a red light before merging onto the freeway, he said.