Seven plug-in vehicles, including the Chevy Volt, qualify for a green sticker in California that enables solo drivers to use carpool lanes in California until 2015.
But barely more than 9,000 stickers have been issued out of 40,000, a slow start considering the previous, now-expired 85,000 yellow decals for hybrids went like hotcakes.
"This program has been around for one full year," said Jan Mendoza, a spokeswoman for the California Department of Motor Vehicles. "Actually 9,000 is pretty good because these are very specialized cars."
The price may be making customers hesitant to buy these more expensive cars. Plug-ins can cost up to $10,000 more than a hybrid, and Californians may not feel confident enough in the economy to splurge.
Clean-air advocates say it's too early to say the results are disappointing, especially when sales toward the end of last year picked up, with nearly 1,400 alone in November.
The goal of cleaner air is still worthy.
"Each clean vehicle on the road means fewer asthma attacks and fewer hospitalizations for serious public health problems," said Bonnie Holmes-Gen, American Lung Association.
With the slow start, the original author of the green sticker program wants to sweeten the pot by giving drivers a couple of extra years in the carpool lane.
State Senator Leland Yee (D-San Francisco) will introduce the bill next week, hoping the extended life in the carpool lane will make up for the price and nudge potential buyers.
"It's a little bit more expensive, and the fact that you can use these particular vehicles in an HOV lane, that kind of helps settle the anxiety about the costs a little bit more," said Yee.
California already has 40 percent of all plug-ins registered in the United States. Yet more than 30,000 green stickers are left.