Caltrans Study Focuses on New Car-Pool Lanes

It may look like just another crowded interstate, but a four-mile swath of the San Diego Freeway running through this community is serving these days as a sort of laboratory.

The unveiling of the microscope took place Friday.

The California Department of Transportation has installed seven videotape cameras atop freeway overpasses between Jeffrey Road and Irvine Center Drive that will be used to study the demeanor of the new set of car-pool lanes that were opened along the freeway earlier this year.

These car-pool lanes, after all, are anything but typical. Instead of the usual double-yellow line separating them from the slow-moving masses, the Interstate 405 commuter lanes have a 14-foot-wide buffer of asphalt between them and general-use lanes.

Caltrans officials are eager to determine if the new car-pool lanes, which are the first of their kind in the United States, will perform better than the old ones. The $48,000 worth of videotape cameras and recorders deployed along the freeway will help with that task, Caltrans officials say.

“What we’re going to look at with these cameras is the operational characteristics of the 14-foot buffer,” said Joe El-Harake, commuter lanes coordinator for Caltrans in Orange County. “Right now, there’s no real design standard for the buffer between the lanes. This is an evolving science. We’re trying to push the limits of design.”

The cameras are mounted on freeway overpasses and feed their pictures to recorders in sealed boxes nearby. Each camera fires off a picture every few seconds, so when the tapes are played at normal speed the movements of cars are speeded up. With this time-elapsed video, a two-hour videotape can last three days before a Caltrans work crew has to install a replacement.

When the tapes are returned to Caltrans district headquarters in Santa Ana, El-Harake and other officials can monitor the disposition of the car-pool lanes with a simple TV screen and VCR, watching three hours worth of traffic rush by in less than half an hour. The tapes also carry the “real time” in minutes, the date and the location where the pictures were being shot.

By monitoring the videos, officials will learn how the car-pool lanes and their revolutionary 14-foot buffers perform. They can count the number of people who risk a ticket by violating the buffer, an offense that carries a $246 fine, and study how well the car-pool lane performs as traffic slows in the mixed-use lanes.

Caltrans officials have been studying the pictures delivered by the cameras for only about a week, and the entire study will continue for another six months. But it already appears that the 14-foot buffers are a significant improvement on the old designs, El-Harake said.

There are fewer violations in the new lane. In addition, the buffer appears to help keep traffic in the car-pool lane moving at a good clip even when the general-use lanes jam up, he said.

With a normal car-pool lane separated by a narrow yellow line, motorists have a natural tendency to hit the brakes when they see traffic slow in the other lanes. But with wide expanse of asphalt separating them from the heavy traffic, motorists in the Irvine car-pool lanes seem to have less reluctance to ease up on the gas pedal when traffic slows in the other lanes, El-Harake said.

Moreover, preliminary results show that the wide buffer acts as more of a deterrent to motorists who might otherwise skip across the double-yellow lines to sneak into the car-pool lane. As deciphered from the videotapes, the violation rate on any given day ranged from less than 1% to 1.5%, well below the current average of 4% on the Costa Mesa Freeway car-pool lanes, which feature a four-foot buffer along most of their length.

“I think this bigger buffer represents a real mental barrier for most people,” El-Harake said. “They just don’t want to risk crossing something that wide. They’re almost behaving as if they have a physical barrier there.”

An offshoot of the improvements, he said, may be reflected by the number of people using the commuter lanes. The San Diego Freeway’s car-pool lanes through Irvine have managed to pick up a large number of users far more quickly than did the commuter lanes on the Costa Mesa Freeway.

During peak periods, about 1,450 cars an hour are using the Interstate 405 car-pool lanes, which opened in May. The lanes on the Costa Mesa Freeway had only about 800 cars an hour after they were in use a half-year, El-Harake said.

Such results have convinced El-Harake and other commuter lanes specialists at Caltrans that the wide-buffer car-pool lane is the wave of the future.

Although the larger buffer cannot prevent accidents--unlike a concrete barrier--they are far less expensive, he said. In addition, a concrete barrier takes up just about as much real estate because of the need for shoulder space.

While the cameras along the San Diego Freeway are providing authorities with rolls and rolls of videotape, none of it is being used by law-enforcement agencies for any purposes, El-Harake said.

But the cameras eventually might play a role in helping to police the freeways. After the car-pool lane study is completed next year, Caltrans plans to install microwave equipment at each overpass so the video pictures can be relayed to monitors in the newly opened Orange County traffic operations center in Santa Ana.

Authorities then will be able to detect traffic accidents or other problems much more quickly and dispatch help.