SAN FRANCISCO (KPIX) — Carpool cheaters beware.

A new study initiated by the Metropolitan Transportation Commission finds that carpool lane violations are widespread and on the upswing — to the point where federal highway funds may be in jeopardy.

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The MTC survey, which was conducted by observers stationed on freeway overpasses at some 83 locations, shows that 24 percent of vehicles in carpool lanes during the morning commute lack the required number of passengers. The violation rate drops to 19 percent during the evening commute.

“It really agitates drivers when they see those people [violators],” California Highway Patrol spokesman Ross Lee told KPIX.

And CHP officers report they’ve heard it all when it comes to excuses.

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“We’ve seen people who are using dummies, [in a] child car seat, or a doll or something else that’s in the car seat,” Lee continued. “Solo mothers driving, commenting that, because they’re pregnant, there are two people in the vehicle.”

The MTC says carpool cheating could collapse the system because federal money could be withheld if the average speed in carpool lanes doesn’t reach 45 mph at least 90 percent of the time. Two years ago, nearly 60 percent of Bay Area carpool lanes failed to meet that requirement, according to Caltrans.

“The traffic is just getting ridiculous and I know why the people are doing that — because the traffic is crazy,” said Ken Way, a Bay Area driver who admitted to some past carpool cheating himself.

One suggestion to reduce crowding is to stop letting solo drivers of electric and low-emission vehicles use the carpool lanes.

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Better awareness of the price of cheating might help too. Carpool scofflaws who get caught will get a ticket for $370 — not including county and court fees.