High Occupancy Vehicle (HOV) lanes encourage carpooling by requiring a minimum number of car occupants, but also inspire a healthy number of detractors who try to game the system: A man who was caught last week with a skeleton in his passenger seat represents a growing epidemic of motorists concocting schemes to avoid the increasing traffic in metropolitan areas.

The creative law-breakers

Drivers are willing to go to all extremes to secure a speedier trip in the HOV lanes. On the show "Curb Your Enthusiasm," Larry David famously picks up a prostitute to sit in the passenger seat so that he can get to a Dodgers game more quickly in the speedier lane.

But beyond the televised interpretation of this phenomenon, the reality can be comical as well.

Some pregnant women, for example, according to police, assert that their unborn fetus constitutes an extra passenger, justifying their right to use the HOV lanes. Candace Dickinson, an Arizona woman who had been fined $367 for driving solo in the HOV lane in 2005 when she was pregnant, is one who tried that defense and failed. The Phoenix Municipal Court found that a "common sense" interpretation of the law holds each person must occupy a separate space in the vehicle.

People go to all sorts of extremes--even putting make-up on mannequins, and stuffing their clothing with newspaper in an attempt at realism. In especially high-traffic areas like greater Los Angeles, Washington DC and Boston where rush-hour traffic is fierce, police still, from time to time, find violators with blow-up dolls, kickboxing dummies, cardboard cut-outs and mannequins. An even easier ploy still being tried--dolls in baby car seats.

"You hear about people using dummies every once in awhile but never skeletons!" said Robert Sinclair Jr., manager of media relations for AAA New York. "I don't think the use of dummies is widespread but they certainly get lots of attention when they are discovered."

Enforcement, though, is necessary.

"If they are not enforced widespread violations occur and the effectiveness of the lane is greatly reduced," Sinclair said. "I think that NJ had a problem with enforcement on their HOV lanes and this was another contributing to them being dropped there back in the 1990s."

The questionable efficacy of HOV lanes

HOV lanes not only accommodate cars with multiple passengers, but drivers of electric cars in some markets. Some areas, such as Los Angeles and Washington DC at one time gave HOV stickers out to owners of hybrid cars to encourage purchase. But too many hybrid sales actually clogged the lanes. The cars that still have the stickers sell for a premium on the used car market.

The benefits of HOV lanes are widely questioned, both from a commuter efficiency perspective and an environmental one.

"There is an understandable backlash against HOV lanes in many large urban areas," said Robert Poole, director of transportation policy at the Reason Foundation. "The problem is that most of these HOV lanes are either too full or too empty."

"HOV lanes are not an effective way of reducing air pollution and could possibly increase pollution by causing more cars to idle in traffic in the non-HOV lanes," said John Nothdurft, director of government relations at The Heartland Institute. "If the purpose of these lanes is to lessen air pollution or reduce traffic then they have failed and states should look at different alternatives such as congestion pricing. One version of this is to convert the typical HOV lanes over to High-Occupancy Toll (HOT) lane." Such lanes would charge those driving alone more than those cars with multiple passengers.

The number of people taking advantage of carpooling is limited. The 2000 U.S. Census found that some 12% of commuters carpool to work. Commuters have upped the ante by in the intervening decade with 518,520 drivers sharing 7,776 vehicles through 27 programs in the U.S., according to University of California, Berkeley researcher Susan Shaheen.