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Kicking hybrids from carpool lanes slows everyone down

October 10, 2011 | 12:50 pm

A single occupant Toyota Prius southbound on the 405 Freeway during rush hours. For good traffic flow, a new UC Berkeley study suggests, that is exactly where you want him to be. Lori Shepler, Los Angeles Times If you're like many California motorists, you probably looked on with envy or perhaps some stronger emotion when those single-occupant hybrids zipped by in the carpool lane. Others who had gone to the trouble of coordinating schedules and establishing real carpool relationships probably weren't too happy with their solitary HOV brethren either.

Surely, fairness was restored over the summer when the interlopers lost their HOV rights; the real carpoolers have seen their speeds increase, right? Wrong.

A UC Berkeley study released Monday says banishing those lone hybrid drivers from carpool lanes is making traffic slower for everyone. As an example, they cited a four-mile stretch of carpool lane on Interstate 880 in Hayward, which has seen a 15% reduction in speed since single-occupant hybrids were expelled since July 1.

What gives?

Researchers at UC Berkeley's Institute of Transportation Studies said they used traffic-flow theories and six months of data from roadway sensors measuring speed and congestion along all freeway carpool lanes in the San Francisco Bay Area to reach their conclusions.

Among other things, the report's authors found that the additional vehicles in the regular traffic lanes slowed speeds substantially. That slower traffic made it more difficult for the carpool drivers to move in and out of the HOV lanes, slowing them down as well. The report's authors were Michael Cassidy, UC Berkeley professor of civil and environmental engineering, and Kitae Jang, a doctoral student in civil and environmental engineering.

They were examing the end of a program that began in 2005 and ended July 1 that gave consumers an extra incentive to buy low-emission cars. By 2011, about 85,000 low-emission vehicles were carrying the coveted yellow stickers that gave them access to carpool lanes.

"Our results show that everybody is worse off with the program's ending," Cassidy said. "Drivers of low-emission vehicles are worse off, drivers in the regular lanes are worse off, and drivers in the carpool lanes are worse off. Nobody wins."

Related:

MTA plans to convert carpool lanes to toll roads

Electric cars to cost more in California

Gasoline prices at or near record highs for autumn

-- Ronald D. White

Photo: A single-occupant Toyota Prius southbound on the 405 Freeway carpool lane during rush hour, before July 1. For good traffic flow, a new UC Berkeley study suggests, that's exactly where you wanted him to be. Credit: Lori Shepler / Los Angeles Times

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