A new era in commuting begins today for clean-air vehicles with new rules that kick solo drivers out of California carpool lanes and uncertainty over how it will impact commute times and traffic.
As of Aug. 14, more than half a million motorists statewide had an active decal on their vehicle to access carpool lanes. California has an estimated 1,171 carpool lane-miles, with 803 miles in Southern California and 366 miles in Northern California, according to a UC Berkeley study.
With more than 35 million total registered vehicles in California, that means 1% to 2% of the vehicle fleet will lose access to the carpool lane, said Antonio Bento, professor of public policy and economics at USC.
But predicting commuter behavior is always tricky, and experts say it will take time to see how the commute will shake out. On some of L.A.’s most gridlocked freeways, the addition of those clean-air cars probably won’t have much impact because conditions are already so bad. Yet those clean-air vehicle owners will likely feel the pain as they lose their carpool privileges.
“Will they just throw up their hands and get in traffic with the rest of us in the three [other] lanes, or will they actually do something else, because they really do value not being in traffic,” said Michael Manville, professor and chairman of urban planning at UCLA.
Clean-air vehicle drivers could change their driving habits and start their commutes earlier to avoid the peak congestion hours. In the most hopeful and optimistic scenario, some motorists who enjoyed the carpool perk might even ditch the freeway altogether and choose another method of transportation, such as the Los Angeles County Metro rail system. But they would have to be pretty committed to clean air to do that.
When Bento first studied the effects of the decal program in 2014, proponents argued it would cause an overall reduction in freeway traffic.
That wasn’t the case then and it isn’t now.
“What ends up happening is that if I create a program that takes one car from those lanes and therefore creates extra space, someone else would immediately refill that space to try to optimize their commute, so to speak,” he said.
In an already gridlocked freeway during peak hour, Manville said, commuters might not even notice one more car that merges in.
Decal holders are also losing a FasTrak discount. FasTrak users who had valid clean-air decals were able to use the I-10 or I-110 ExpressLanes at a 15% discount under a program administered by the California Department of Motor Vehicles, according to the Los Angeles County Metropolitan Transportation Authority. But the offer is sunsetting along with the decal program on Wednesday.
The Los Angeles County Metropolitan Transportation Authority said it doesn’t anticipate a significant uptick in the number of FasTrak transponders being issued as a consequence of the decal program’s end.
“Through the first nine months of 2025, we have seen between 2,200 and 3,000 new accounts opened monthly,” LA Metro stated in an email. “We anticipate the current trend in new accounts to remain consistent moving forward.”
Whatever new commuter behavior decal holders decide on, they will have a 60-day transition period starting Wednesday “during which drivers with a valid clean-air decal will not be cited for driving alone in the carpool lane,” according to the California Highway Patrol.
“After that, driving solo in the carpool lane could result in a citation,” the agency said.
The carpool lane perk was an incentive used to promote the adoption of clean and zero-emission vehicles in California.
Gov. Gavin Newsom signed a bill last year that would have extended the decal program until 2027, but the bill needed a sign-off from both Congress and President Trump. It got neither.
Newsom has since called the end of the program a “Trump traffic jam.”
“More traffic and more smog is on its way to California, thanks to Trump and the Republican-led Congress,” Newsom said.
The goal of allowing clean-air vehicle drivers into the carpool lanes was to promote the purchase of alternative-fuel vehicles and assist in meeting environmental goals that included reducing fuel consumption and pollution caused by congested freeways, according to the U.S. Department of Energy.
“The result is that today, nearly 25% of all new vehicle sales in California are zero emissions qualified vehicles,” said John Swanton, spokesperson for the California Air Resources Board.
A total of 13 states, including California, developed their own type of incentive program — choosing which car models should get universal access to carpool lanes. Without federal approval, programs across the nation will come to an end.
Bento, who first analyzed California’s program and published his findings in the American Economic Journal: Economic Policy in 2014, concluded that the program which allowed clean-air vehicles access to the carpool lanes was an inefficient way of promoting clean-air vehicles.
“You [were] basically asking those that were already carpooling, and to a certain extent, already emitting less [emissions] relative to a car that has a single driver, in all the other lanes to slow down for these cleaner cars to enter the carpool lane,” he said.
The program, Bento argued, was designed as an “environmental incentive but it didn’t deliver meaningful carbon dioxide emission reductions,” because HOV lanes crowded a mix of gas-fueled and clean-air vehicles translated to an increase in pollution.
“Ending it removes a costly perk that slowed carpools without helping the climate,” he said.
The shift will likely provide some extra elbow room in the carpool lanes and possibly inspire more drivers to carpool once again, experts say.
Bento said he doesn’t believe the end of the decal program will slow down the number of electric vehicle purchases because California has several rebate, tax credit and voucher programs to incentivize that.
Programs like the decals, Bento argued, shouldn’t last forever.
“They should be in place as a way to incentivize earlier adopters, and eventually they need to be phased out. Otherwise they become unsustainable,” he said.
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