skip to main content









Donation Heart Ribbon

How ‘Green’ Are Carpool Lanes?

— Add more lanes to a freeway and you’ve got more cars and more traffic. But what if those two more lanes are carpool lanes?


Aired 6/20/11

Interstate 15 in San Diego will provide more room for carpooling. But that won't necessarily be a win for environment.

The question comes up as CALTRANS closes its carpool lanes on I-15 in San Diego this week so it can add two more, which will be open a week from today.

Interstate 15 is getting two new express lanes in SD County. They'll be ready...
Enlarge this image

Above: Interstate 15 is getting two new express lanes in SD County. They'll be ready for use in about a week.

One thing to keep in mind: Carpool lanes in San Diego are actually called express lanes because they aren't restricted to vehicles with two or more passengers. Solo drivers can use them if they pay a fee.

This has caused some clever people to call them “Lexus lanes.” It also means the lanes don't reduce vehicles trips, or greenhouse gas emissions, as much as they would if they were only for high-occupancy vehicles (HOVs).

Gustavo Dellarda is the CALTRANS corridor director for I-15. He can’t say whether two additional express lanes will reduce or increase car trips on I-15.

“But I can tell you that 80 percent of the vehicles on the express lanes have more than one person in the vehicle,” he said.

Elyse Lowe is director of Move San Diego, which lobbies for mass transit and pedestrian safety. She said the downside of express lanes is they don’t have as great an impact on traffic as HOV lanes. The upside is they raise money, through fees, for maintenance and mass transit.

“It's good to have some kind of revenue to pay for the maintenance of those. But at the same time we need to never, ever, ever allow congestion in those express lanes due to single-occupancy vehicles,” said Lowe.

Simply reducing congestion on freeways can reduce greenhouse emissions. Dellarda said if congestion becomes a problem, CALTRANS will make the managed lanes on I-15 HOV-only.

To view PDF documents, Download Acrobat Reader.


Avatar for user 'Derek'

Derek | June 20, 2011 at 1:39 p.m. ― 5 years, 9 months ago

"She said the downside of express lanes is they don’t have as great an impact on traffic as HOV lanes."

False. In fact, the exact opposite is true. HOV lanes have little to no long-term effect on traffic congestion, while express lanes permanently eliminate congestion. See:

( | suggest removal )

Avatar for user 'timsd'

timsd | June 20, 2011 at 2 p.m. ― 5 years, 9 months ago

If the lanes are filled, the lanes switch to HOV Only. More carpools equals less use by us single drivers with FastTrak. Having the option to sell the space to single riders is best use of a resource.

( | suggest removal )

Avatar for user 'Tom Fudge'

Tom Fudge, KPBS Staff | June 21, 2011 at 1:02 p.m. ― 5 years, 9 months ago

My paraphrase of Elyse Lowe, when she speaks of the effect on "traffic," does not refer to congestion by rather to car volume. Express lanes probably do have a greater positive impact on "congestion." But by giving solo drivers more opportunity to use the freeway at rush hour they do not cut down on car trips or miles driven... perhaps not at all but certainly not as much as HOV lanes. Congestion does increase greenhouse gas emissions. But the bigger issue is vehicle trips and miles driven. The second point about express lanes being the best use of resources may be true. It depends what is your goal; reducing vehicles miles or reducing congestion and raising money for traffic infrastructure.

( | suggest removal )