Study finds that banning hybrids from HOV lanes increases traffic

Researchers from the University of California at Berkeley have found that banning hybrids from HOV lanes increases traffic across the board - including in the HOV lane.

Transportation researchers at the University of California at Berkeley have come up with some surprising results on HOV lanes and hybrids: allowing hybrids to drive in HOV reduces traffic congestion for everyone.

Until last July hybrid car owners in California could ride in the HOV even if they were driving alone. However, the California Department of Motor Vehicles ended that scheme this past summer sending around 85, 000 cars back to regular freeway lanes.

A new study that examined six months of data from roadway sensors that measured speed and congestion on San Francisco Bay Area carpool lanes, however found that the decision may have been a bad idea. Freeway traffic had since slowed down across the board - including the carpool lane (which were 15 percent slower).

While that seems counter-intuitive, the authors speculate that car pool drivers were likely to slow down if traffic in the adjoining lanes was significantly slower, out of safety concerns.

"As vehicles move out of the carpool lane and into a regular lane, they have to slow down to match the speed of the congested lane," said Kitae Jang, one of the researchers. "Likewise, as cars from a slow-moving regular lane try to slip into a carpool lane, they can take time to pick up speed, which also slows down the carpool lane vehicles."

Cassidy also added that drivers were likely to be nervous going 70 mph around slow moving traffic, out of fear that a regular-lane driver may suddenly enter their lane.

The study was done with data from 6 months, so more time may be necessary to see the full effect of the move.

Find the research here.

This post was originally published on


You have been successfully signed up. To sign up for more newsletters or to manage your account, visit the Newsletter Subscription Center.
See All
See All