California plans to tax fuel-efficient cars for not using as much gas.

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"Drivers will get charged for how many miles they use the roads, and it's as simple as that," says engineer David Kim.

College student Jayson Just commutes an odometer-spinning 2,000 miles a month. As CBS News Correspondent Sandra Hughes reports, his monthly gas bill once topped his car payment.

"I was paying about $500 a month," says Just.

So Just bought a fuel efficient hybrid and said goodbye to his gas-guzzling BMW.

And what kind of mileage does he get?

"The EPA estimate is 60 in the city, 51 on the highway," says Just.

And that saves him almost $300 a month in gas. It's great for Just but bad for the roads he's driving on, because he also pays a lot less in gasoline taxes which fund highway projects and road repairs. As more and more hybrids hit the road, cash-strapped states are warning of rough roads ahead.

Officials in car-clogged California are so worried they may be considering a replacement for the gas tax altogether, replacing it with something called "tax by the mile."