Some states are considering taxing motorists by the distance they drive, which would help them in collecting more revenue.

About 25 per cent of price paid by consumers for gas goes to the government which uses it for development and maintenance of highways. And fuel efficient cars would reduce the revenue which would make them good for drivers but bad for the roads.

Experts estimated that such cars could give up to 75 mpg in the city and about 50 mpg on highways. The rising price of gas could lead to more consumers selecting fuel efficient vehicles which would cut down the revenue, it said.

The method being considered is every time a car is filled up, the tax would be charged. A computer in the gas station would communicate with the odometer of the car to determine how much the person filling the gas owes as tax on the basis of miles he had driven since the last filling. GPS systems would also be used to track vehicle mileage.

California is considering replacing gas tax with the “tax by mile” and neighboring state of Oregon has already started road testing the idea.

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

Kim and his team at Oregon State University equipped a test car with a global positioning device to keep track of its mileage. Eventually, every car would need one.

The system could track how often you drive during rush hour and charge higher fees to discourage peak use, it said.

“We’re getting a lot of interest from other states,” said Jim Whitty of the Oregon Department of Transportation. “They’re watching what we’re doing.”