Honeywell Global Turbo Forecast projects 49M turbocharged vehicle sales, $12B revenue per year by 2019
Chinese scientists unveil liquid-phase 3D printing method using low-melting-point metal alloy ink

Study finds solo hybrid drivers in California HOV lanes amplify congestion, create up to $4,500 per car in adverse social costs annually

Allowing single-occupant low-emission cars in California to use high-occupancy vehicle (HOV) lanes on congested highways exacerbates the congestion and causes up to about $4,500 per car in adverse social costs annually, including increased commute times and carbon dioxide emissions, according to a new study in the American Economic Journal: Economic Policy.

The authors, from Cornell University, University of Colorado, UC Irvine and UC Berkeley, calculated that the Clean Air Vehicle Stickers (CAVS) policy results in a best-case cost of $124 per ton of reductions in greenhouse gases; $606,000 per ton of nitrogen oxides reduction; and $505,000 per ton of hydrocarbon reduction—exceeding those of other options readily available to policymakers.

The California law enabling single-occupant access to the HOV lanes was meant to stimulate sales for fuel-efficient, ultra low-emission vehicles, with the goals of reducing dependence on foreign oil and saving money at the gasoline pump. Between August 2005 and June 2011, California law allowed owners of hybrid vehicles achieving at least 45 mpg (5.2 l/100 km) to purchase a Clean Air Vehicle Sticker for $8, allowing them to drive on carpool lanes regardless of the number of occupants in the car. However, two-thirds of the sticker registrants had hybrid cars already on the road, the authors noted; in other words, the stimulus effect was lower than expected.

While the original clean air sticker policy expired in 2011, a new HOV-exception program with 40,000 stickers for electric, hydrogen fuel cell, and plug-in hybrid vehicles started in 2012.

While adding a single hybrid to any HOV lane at 2 a.m. creates no congestion or social costs, said the researchers, adding one hybrid driver at 7 a.m. on weekdays to an already congested road such as Interstate 10 in the Los Angeles area appends $4,500 per car in annual costs (in pollution and time) to society.

With the addition of solo-driver hybrids on already congested highways, HOV lane traffic climbs above 30% beyond socially optimal levels, according to the research. Thus, carpooler congestion costs substantially outweigh the green benefits of hybrids, the researchers concluded.

The economists suggested several alternatives:

  • Instead of letting the solo-driver hybrids into rush-hour carpool lanes, the state should provide a tax credit for hybrid vehicles, much like the federal government.

  • Policymakers could ration HOV access via congestion pricing, which could relieve congestion and improve air pollution.

  • Having commuters use buses may represent the win-win in terms of pollution and congestion that policymakers were hoping with the CAVS [sticker] policy, the researchers suggested in the paper.

Even if vehicles were truly zero emission, policies that promote their adoption at the expense of exacerbating congestion still generate substantial losses of time for high-occupancy vehicle commuters, they explain in the paper.

To reduce congestion in that interstate corridor and to be fair to commuters in high-occupancy vehicles, the economists suggest a congestion toll of 45 cents per mile, and for hybrid and low-emission vehicles, a reduced congestion toll amounting to 38 cents per mile.


  • Antonio Bento, Daniel Kaffine, Kevin Roth and Matthew Zaragoza-Watkins (2014) “The Effects of Regulation in the Presence of Multiple Unpriced Externalities: Evidence from the Transportation Sector,” AEJ: Policy Volume. 6, Issue 3 doi: 10.1257/pol.6.3.1



Fuel for the right-wing, PEV hating, global warming denying media!


There are many solutions available:

1. Phase out and/or charge more for all ICEVs.

2. Share e-vehicles and allow on free lanes.

3. Allow e-buses on free lanes.

Patrick Free

I don't understand why California does not restrict this access further to push further the green cars of the future. In addition to pushing all EV cars, they should create an interim step for Optimal PHEVs, that for me have at least 30KWH battery pack, dropping all Hybrids set with a too small battery, and that at the end do not allow to do all local commutes in all electric mode properly. Reason for 30KWH is simple, this allows to make 100 Miles on a charge in a very comfortable all electric mode. And since my daily local commutes are only taking 50M, this would allow me 1 charge every 2 x days only. And this is key because 1 charge every 2 days makes a good quality 3000 x cycles battery last up to 20 years (15Y may be the maximum due to other wearing factors after 10 years, but that is still the life time of best current cars, so no battery replacement required with 30KWH. That is a lot greener !).


When you analyze the whole idea of commuting to work on congested highways in single occupant vehicles, it's a senseless failure except for oil and car company profits.

Mass transportation using electric machines is the better idea.


So adding hybrids to already overcrowded non-HOV lanes saves $4500 per vehicle per year of social costs...?


If you follow the link, this study cherry picks Los Angeles. The numbers are probably different in other parts of California.

Also, like @kelly mentions, it doesn't address the negative impact of putting more traffic in non-HOV lanes.

However their suggestion of scrapping preferential HOV access and providing tax credit does have merit if its the more effective policy.

Voters are likely to be very hostile to "per mile" congestion charges because that implies a "Big Brother" monitoring system in your car. The federal government has already been caught in data gathering abuses. I doubt that one will fly.


FedGov is already building data-gathering abuses into the V2V and V2I data architecture.  Good luck with that one, short of burning it all down.  New slogan:  "Those who make reasonable accomodations impossible, make extreme responses inevitable."

If virtual presence ever gets good enough that people work from home while still being "at" the office well enough to suit managers, the commute could disappear very suddenly.  Optical fiber is a lot less energy-intensive than motor vehicles.  Then again, the end of distance has been predicted for some time yet failed to appear; don't bet on this until it makes real inroads.


It does seem like a garbage study. Are they saying the carpool lanes are congested? Then this freeway is screwed up to begin with. Why people put up with LA traffic is beyond me.


Garbage study indeed. HOV lanes were created to fulfill a need (moving a higher number of commuters per mile-hour during rush hours). How could that need suddenly have evaporated because hybrid vehicles exist? Has it not dawned on some people that more HEV's, PHEV's and all just means -- more cars on the road?

Ford Prefect

"While the original clean air sticker policy expired in 2011, a new HOV-exception program with 40,000 stickers for electric, hydrogen fuel cell, and plug-in hybrid vehicles started in 2012."

Somebody really needs to do some fact verification. EV, H2, and (not listed) CNG vehicles have had a program in place longer than 2012 AND have unlimited decals available. PHEV vehicles have a cap that keeps getting extended.


I do not see where they are getting the $4500 number. There was a study done at U.C. Berkeley that showed car pool lanes cause congestion in the SFO Bay Area. The lanes were under used causing more congestion.

If that is the case, the HOV lanes get more use with hybrids, which reduces overall congestion. The cars are going to be there no matter what, people need to get to work. Car pools are seldom used, that was the original idea for the HOV car pool lanes to begin with.

The comments to this entry are closed.