When California legislators opted last year to allow single-occupancy HOV access for hybrids to lapse, the reasoning was pretty straightforward, and many green vehicle advocates took it in stride. The program had run its course, lawmakers said. With the maximum of 85,000 yellow hybrid Clean Air Vehicle stickers already having been issued and hundreds of thousands of hybrids already on California roads, there was no reason to continue a program that prospective new hybrid owners weren’t even eligible for. More importantly, advocates for the decision to not extend the program said that HOV lanes had become too crowded, reducing the advantage for both carpoolers and clean vehicle owners.
The state also had an interest in incentivizing the newest frontier in low-emissions driving: plug-in cars. Last summer, Governor Schwarzenneger signed AB 1500, which extended the HOV rights already enjoyed by electric vehicle owners—who have been eligible for white Clean Air Vehicle stickers since the start of the program—through January, 2015. In theory, electric vehicles and certain qualified PHEVs would eventually come to replace hybrids in the carpool lane, and in the meantime, multiple-occupancy vehicles and early plug-in adopters would enjoy an even clearer commute than before.
But just months into the yellow sticker expulsion, a study by researchers at the Institute of Transportation studies at the University of California Berkeley is calling into question one of the basic premises of the decision to kick hybrids out of the HOV lane: that the program was slowing traffic for carpoolers. In fact, the study claims the program had a significantly positive effect in evening out the traffic flow during high-congestion periods, and may have even led to a quicker commute for all HOV-eligible vehicles.
Wrote (PDF) study authors Kitae Jang and Michael J. Cassidy:
“These [Low Emissions Vehicles] invariably constitute small percentages of traffic; e.g. they are only about 1% of the freeway traffic demand in the San Francisco Bay Area. Yet, we show that relegating some or all of these vehicles to regular-use lanes can significantly add to regular-lane congestion, and that this, in turn, can also be damaging to vehicles that continue to use the carpool lanes.”
How could decreasing number of cars in HOV lanes actually have the unintended effect of slowing down the speed of traffic in those lanes? Jang and Cassidy theorize that significantly increased congestion in non-carpool lanes has a psychological effect on HOV drivers, causing them to slow down due to the perceived danger of traveling quickly during times of high congestion. Though the researchers were unable to conclusively isolate a single root cause of the phenomenon, six months of data finding a 10-percent longer average commute time since the expiration of the yellow Clean Air Vehicle stickers seems to back it up.
So were lawmakers hasty in eliminating a hybrid perk that by one estimation added between $1,200 and $1,500 to the resale value of eligible hybrids? Despite good intentions, perhaps they should have waited until there were enough plug-ins on California roads to displace the added congestion.