But the big losers could be motorists who now use the carpool lanes for free. Carpoolers would also have to pay a toll, possibly reduced. Also, the proposal provides no toll exemptions for hybrid vehicles that can now use carpool lanes regardless of the number of passengers.
The concept doesn't sit well with some carpoolers and others, who argue that the lanes should remain free for ride-sharers, which they say reduces pollution and traffic.
"I think it's a horrible direction to go and I think it's immoral to sell the diamond lanes," said Charles Tarlow, a Mid-City resident. "I also think it's outrageous that the feds take the position that they'll give us millions of dollars for lanes that exclude people who can't afford to pay for congestion pricing. If they want to help, let's get some mass transit in here -- and if they want mass transit, then let's have taxes for that."
Karen Leonard, a UC Irvine professor who uses the 405 carpool lanes to commute between her home in Cheviot Hills and Irvine, said she's concerned but wants to see what the price would be.
"I asked my carpool buddy . . . what he and I would be willing to pay if the carpool lane went toll and he said certainly $5, but not as much as $20," said Leonard. "We'd be willing to pay because the carpool lanes have made a big difference."
The Metropolitan Transportation Agency's initial plan would not cover the 405 but would include carpool lanes on the 110 Freeway in South L.A. as well as the 10 and 210 freeways in the western San Gabriel Valley.
The idea is part of plans by the MTA and Caltrans to implement "congestion pricing" in L.A.: charging a toll to use certain roads in return for faster speed. The toll prices would rise during rush hour.
The concept quickly gained steam in November after the U.S. Department of Transportation said it would give out more grants to fund such projects.
L.A. missed out in the last round of grants issued in August because local officials did not seriously consider such a congestion pricing plan in the county's last federal application.
"We're just too congested to turn our backs on that kind of opportunity," said Carol Inge, chief planning officer for the MTA. The cost of the toll lane conversion could be about $100 million, Inge said.
Officials said the plan would not only add revenue to shore up the region's crumbling roads, but help manage traffic congestion on the converted carpool lanes. As the tolls rise during peak hours, penny-pinching commuters may opt to use the regular lanes, freeing up space in the toll lanes.
Those who pay the higher toll win the prize of a shorter commute.
"We've all decided as a society we're not going to add massive levels of new freeways through our urban areas to reduce congestion," said Doug Failing, director of the Caltrans office overseeing L.A. and Ventura counties. "If you're not going to increase the supply, you've got to control the demand."
Failing said the concept is familiar to anyone who buys a plane ticket. It's far more expensive to fly during the Thanksgiving holiday than during an off-peak period. The same financial incentive should work for local freeways, he said.
Converting carpool lanes into toll roads is far from a done deal. Failing said Caltrans and the MTA need to make sure it's profitable to install and maintain the tolling system.
They will also need to win the support of the California Transportation Commission and the federal grant. The grant application is due Dec. 31.
Implementing the idea is sure to be controversial. People who currently travel toll-free in carpool lanes and are unwilling to pay a fare might begin crowding into regular freeway lanes.
That is likely to be a problem on the San Bernardino Freeway's El Monte Busway, one of the most congested carpool lanes in the country.