They're red. They're green. They're red again.

They're the last thing motorists on a freeway onramp want to see: another signal, but one that is never green when you get to it.

In an age when building or widening freeways isn't possible or is prohibitively expensive, ramp metering lights are increasingly seen as the path to relieving traffic congestion.

That's especially true on the Bay Area's most-congested stretch of freeway, Interstate 80 from Hercules to the Bay Bridge Toll Plaza. Traffic engineers are planning to make the on-again, off-again traffic signals the linchpin of an $88 million plan to squeeze the maximum efficiency out of the interstate, which can't be widened without destroying the swath of civilization built up against its noise barriers.

The lights do two key things: They parcel out traffic so that the freeway won't get clogged as easily, and they space out vehicles so cars can merge with freeway traffic more smoothly.

But even 45 years after the first ramp metering was tested by police officers waving traffic onto Chicago's Eisenhower Expressway, some Bay Area officials are still skittish about impeding freeway access.

"It's been kind of an uphill struggle in the Bay Area,"' said Albert Yee, director of Highway and Arterial Operations for the Metropolitan Transportation Commission. While the commission is attempting to promote and finance a $600 million area-wide system favoring more metering lights to help move traffic more efficiently, some officials in Contra Costa have resisted the effort.

The lights have met resistance elsewhere, too, such as in Santa Clara County in the 1990s, but eventually, results have won the lights some grudging acceptance.

Metering lights are an old staple on Southern California freeways, where the state transportation department, Caltrans, is testing the next generation of metering systems on the Interstate 210 Foothill Freeway from Sylmar to Pasadena to San Bernardino.

The commission's staff and Caltrans are attempting to get officials in nine Bay Area counties to endorse the installation of metering lights in order to create an area-wide traffic control system.

In January, the effort got a big boost when Caltrans turned on metering lights on eastbound Interstate 580 through Pleasanton and Livermore. That stretch of freeway is continually competing for the second- or third-worst-congested segment, after the westbound morning commute on I-80.

"Anybody who's driven the Altamont (Pass) in the afternoon knows how bad it is," Yee said. Since the lights were turned on, congestion, or excess travel time, has been cut in half.

The lights reduced average peak travel times from the I-580/I-680 interchange in Pleasanton to the eastern end of Livermore from about 40 minutes to about 25 minutes. With the lights working, congestion also starts about an hour later and ends a half-hour earlier.

"With a small amount of money, you get a huge amount of congestion relief," Yee said. Putting in lights and reconfiguring seven onramps costs less than $20 million, he said, while "to widen the freeway for that stretch, you're talking about a price that's 10 times more, on the conservative end (and) probably 10 to 20 times more."

A dim view

Santa Clara County is getting $2 million from the commission to help fill in gaps in metering coverage on U.S. 101 and state highways 85 and 237 in the San Jose area. Yee's staff is also working with Solano County officials on a ramp metering plan, while Marin officials are considering new meters on U.S. 101 in spite of older, shorter ramps. The Metropolitan Transportation Commission is developing a regional transportation plan that proposes to spend roughly $100 million on the lights as part of its $600 million program to make freeways more efficient.

But in Contra Costa, key transportation officials view the lights with skepticism, if not disdain.

"The more you meter the ramps, the more difficult it is for local people to use the freeway," said Robert McCleary, executive director of the Contra Costa Transportation Authority. "For example, people in Berkeley or Albany or Emeryville are not going to want to be metered so that people from Contra Costa can have an easier trip."

The problem, McCleary fears, is that where ramps are short and metering intervals long, traffic will back up locally, negating the benefits for anyone who isn't simply passing through the area.

The results on eastbound I-580 were particularly good, McCleary believes, because that freeway has long stretches where the bulk of the traffic is passing through, and onramp traffic is limited. Metering on I-80, I-680 and state Highway 4 through his county pose more difficulties, he believes.

The county's lingering doubts have left metering lights dark for several years on state Highways 4 and 242, between Concord and Antioch. Caltrans mandates their installation with any new freeway work, but turning the lights on requires traffic studies and agreement from local authorities.

Even proponents of the meters acknowledge that places where there are no parallel local roads to accommodate excess freeway traffic can put a damper on a metering scheme. According to Yee, the metering plan for I-80 includes modifications to help improve flow on San Pablo Avenue, a major artery that parallels the length of the Eastshore Freeway, to address this.

McCleary said he would like to see metering lights synchronized with local traffic signals, so that when traffic backs up locally, the floodgates onto the freeway will open up.

"We are going to have to manage the freeways," McCleary concluded. "But it may not just be ramp metering, but also pricing," which follows a national movement to make motorists pay tolls for freeway use during the most-congested periods. "There are very difficult political choices to be made about who gains, who doesn't gain."

Easing the flow

In San Mateo, metering seems to be working just more than a year after Caltrans turned on the lights on U.S. 101.

Beyond some initial equipment snafus, "it's actually functioned very well," said Larry Patterson, the city's public works director. Patterson said there hasn't been much diversion of freeway traffic onto local streets, except for short trips, which the meters are supposed to encourage.

San Mateo Mayor Carole Groom finds they've actually made it easier to get onto the freeway. The lights have left people "feeling a little safer about being able to merge into the lane you want," she said.

If local traffic is the issue, then metering lights should be welcome, said Thomas West, director of the Center for Innovative Transportation at UC Berkeley.

"The better that (freeway) system performs, the less chance that people will get off that system and drive by my house," he said.

"The highways are designed to carry a certain amount of cars, period. If you have one or two more vehicles, it's like the proverbial straw that broke the camel's back," West said. After the freeway exceeds capacity, it's like kindergartners all trying to rush into the same doorway at once: There's a knot and nobody gets through quickly.

On the freeway, West said that means the speed curve, or ratio of traffic volume to flow, "drops off the face of the earth."

Keeping those volumes just out of the danger zone could be accomplished even more efficiently with the new generation of metering, which will be a key part of a centralized, regional traffic management system. Sensors currently track much of the area's freeway traffic, but the next generation system will sync all that up with metering lights and additional message boards with traffic information, said John Wolf, a Caltrans assistant division chief who deals with planning traffic management systems.

The idea has already been tested in computer modeling, and now Caltrans is using the length of Southern California's I-210 to see how carefully feeding traffic into the entire length of the freeway will keep it flowing better.

"The result of ramp metering is better travel time overall, even with delays on ramps," Wolf said. The system is similar to synchronized traffic lights on city streets, feeding traffic through at a prescribed rate to prevent everyone converging on the same place at the same time.

Strategies to regulate traffic, such as metering lights, tolls, sensors and traffic information signs are vital to getting the most out of the freeways, according to West.

"There's unending things that can be done," West said. "The question is, do we have the guts to do it?"

Reach Erik Nelson at 510-208-6410 or enelson@bayareanewsgroup and read the Capricious Commuter blog at InsideBayArea.com.

Ramp metering 101

Metering lights in common use today use sensors in the main freeway lanes to determine when traffic is approaching capacity. Then a traffic signal at a nearby onramp is activated, allowing one or more (usually one) cars for every time the light turns green. The length of the red signal is regulated by the traffic flow on the main line of the freeway, but when lines on the ramp become so long they may impede traffic, a queue sensor forces the metering lights to allow vehicles through faster to shorten the line.

A state-of-the-art system being tested on Interstate 210 in Southern California uses traffic sensors the entire length of the freeway to determine how quickly cars should be allowed past the ramp meters.

The purpose of lights is threefold: One, to keep freeway traffic from exceeding capacity and backing up; two, to put space between vehicles to ease merging; and, three, to discourage short freeway trips.