By San Francisco Business Times

Banning hybrid vehicles with just one person in them from carpool lanes in the Bay Area was a mistake, according to a University of California, Berkeley study.

Back in 2005, California gave solo drivers of hybrid cars the right to use carpool lanes on freeways, but by this summer, when some 85,000 hybrids were on the roads in the Golden State, the program ended.

Critics said hybrid cars were clogging up carpool lanes and slowing down the commutes of carpool vehicles.

But researchers at the Institute of Transportation Studies, or ITS, at U.C. Berkeley found that now everyone is worse off.

Michael Cassidy, a civil and environmental engineering professor at Cal, and doctoral student Kitae Jang studied six months of data from roadside sensors and mathematical models to predict -- even before the change in July -- that kicking hybrids out of carpool lanes would slow things down for everyone. More data they collected after July 1, when hybrid drivers were denied the perk, confirmed their prediction.

⿿Our results show that everybody is worse off with the program⿿s ending,⿝ said Cassidy. ⿿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.⿝

Looking at a four-mile stretch of Interstate 880 in Hayward the researchers found that after July 1, when solo occupant hybrids couldnâ¿¿t use it anymore, average traffic speed in the carpool lane fell by 15 percent.

Why the counterintuitive result?

Although speed in a carpool lane is affected by how many cars are using it -- thus it might move faster with fewer hybrids -- it is also affected by how fast adjacent lanes of traffic are moving. And with the exiled hybrids in them, those lanes are moving much slower.

⿿Drivers probably feel nervous going 70 miles per hour next to lanes where traffic is stopped or crawling along at 10 or 20 miles per hour,⿝ said Cassidy.

Now, the only cars allowed in carpool lanes with a single driver are a few that use hydrogen fuel cells, are 100 percent battery electric, or burn compressed natural gas.

Even a new federal program that would allow 40,000 more super-clean plug-in-hybrids or hydrogen powered internal combustion vehicles into carpool lanes wonâ¿¿t be enough, Cassidy and Jang found.

Read the study here.

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