Anyone who has ever driven in one of the 19 states with carpool lanes can relate to the frustration of being stuck in traffic and looking over to an H.O.V. lane that seems empty.

Click in the video box to the right to watch a report by FOX News' Dan Springer.

A few can even relate to being the lucky one in the H.O.V. lane watching the poor souls stuck in standstill traffic.

Now, Washington state has done the unprecedented. It has taken one of those under-utilized lanes and opened it up for everyone.

The now-unrestricted carpool lane was built five years ago on Interstate 5 near Vancouver, Wash, a main artery carrying people to work in nearby Portland, Ore.

From the beginning, the lane was barely used and did nothing to ease congestion or speed up travel for those who were able to use the H.O.V. lane. Drivers rebelled, and after a lengthy study confirmed the problems, the state Transportation Department converted the lane to general purpose.

But not everyone is pleased with the decision. Environmental groups say the move is short-sighted.

"Opening up the carpool lane is not going to solve traffic problems for the people who are stuck on the freeway," said Aaron Ostrom, executive director of FutureWise. "What it's going to do is eliminate choice for bus riders and carpoolers to have a reliable alternative to being stuck in traffic."

Carpool lanes are labeled a success by those who cite studies that show even though fewer vehicles are H.O.V.-designated, they are carrying more people than the adjacent lanes during rush hour. By providing quicker commutes, cars are also getting off the road more quickly, which means less air pollution and less fuel consumed.

Commuter groups argue that H.O.V. lanes increase traffic congestion by taking away up to a third of available space. State highway officials also have expressed some worries that eliminating carpool lanes will remove the best motivation to keep the extra cars off the road.

"If all of the people who were using carpools, vanpools or taking the bus now were instead single-occupant drivers, congestion would be far worse," said Charles Prestrud of the Washington Department of Transportation.

But critics of carpool lanes say they, like all transportation projects, need to focus on making travel quicker for all commuters, not just an elite few.

"They are wedded to this idea that you measure progress by getting people out of their cars. If it means more congestion to make them do so, so be it," said John Carlson, talk radio host on KVI Radio in Seattle.

By all measurements, congestion in the Puget Sound, as well as the rest of the country, is getting worse.

Locally, there are 200 H.O.V. miles with 100 more miles on the drawing board. A federal study showed that during the 1990s, while the United States was quadrupling the number of carpool lane miles to more than 3,000 nationwide, the percentage of commuters who drove alone during that time also went up.