Proposed new rules in the US may knock some hybrid vehicle models out of the so-called high-occupancy vehicle (HOV) lanes on motorways.

The government has proposed new criteria for certifying vehicles as clean and energy efficient – standards for states that let hybrid drivers travel without passengers in the special lanes to avoid rush-hour traffic, The Associated Press (AP) reported.

States typically restrict high occupancy vehicle, or HOV, lanes to conventional vehicles with two or more people during designated hours but let hybrids use them, a move that has attracted criticism from harassed commuters.

But, under the new proposals, the driver of a hybrid would qualify for HOV lanes during peak time only if the vehicle can achieve 25% higher combined fuel efficiency for city and highway driving compared with similar petrol-fueled vehicles.

Only four manufacturers – Toyota, Honda, Ford and Mazda – make vehicles that would qualify, AP said, adding that a limited number of natural gas vehicles built by Honda and Ford also would meet the standards.

The qualifying vehicles include: the 2004-07 Toyota Prius, 2006-07 Toyota Highlander Hybrid, 2006-07 Lexus RX400h, 2006 Mazda Tribute Hybrid, 2005-07 Ford Escape Hybrid, 2006-07 Mercury Mariner Hybrid, 2003-07 Honda Civic Hybrid, 2003-06 Honda Insight and 2005 and 2007 models of the Honda Accord Hybrid. Natural gas versions of the 2003-05 Honda Civic and 2003-2004 Ford Crown Victoria would apply, too.

However, the list of vehicles that would not qualify include the luxury Lexus GS450h Hybrid, Dodge Ram Hybrid and Saturn Vue Greenline Hybrid.

Auto industry officials were reviewing the proposal and declined immediate comment to the news agency.

AP said the proposal seeks to balance the government’s interest in promoting the fuel-efficient vehicles with concerns that an influx of hybrids could clog up car pool lanes in congested cities.

It noted that most states require HOV lanes to carry two or more occupants but a federal highway bill signed in 2005 allowed an exemption for fuel efficient vehicles carrying only the driver. The new criteria was developed for the Transportation Department, which administers HOV programmes.

The EPA measure allows states to choose stricter rules. California, which has an estimated 140,000 hybrid registrations, requires the vehicles to get 45 mpg to use HOV lanes, AP noted.

A spokesman for the Union of Concerned Scientists told the news agency the proposal would encourage the “best and the brightest” of the hybrid choices instead of “allowing muscle hybrids or hybrids that are not really using the technology to push the envelope.”

Hybrids also could qualify as energy-efficient by achieving 50% or better in-city fuel economy. Dedicated alternative fuel vehicles could qualify, too, to use the lanes, AP added.

To be considered low emission, the EPA said the vehicles would need to meet federal and [stricter] California emissions standards, according to the Associated Press.

Scott Stapf, executive director of the Hybrid Owners of America, said 37 states have the hybrid HOV provisions or are studying the concept.

“This is a pretty hot topic at the state level,” Stapf told AP. “Hopefully this will help.”