(CBS) — The idea of the state of Illinois imposing a mileage tax on vehicles in place of the current gasoline tax was met with big opposition last week and the idea was dropped. But one state is already trying it.

Oregon has had a road usage charge since last July. There are no more than 5,000 motorists allowed to take part, during what Oregon Department of Transportation spokeswoman Michelle Godfrey calls, “a final test drive.”

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In the end, she says, that’s how Oregonians will be paying to maintain roads.

“It’s really a modern way to do it,” she says.

Godfrey points out that, “vehicles are getting more and more fuel efficient and that’s terrific. It’s certainly something we want to encourage for our environment and for loosening our dependency on fossil fuels, but we also need to decouple our funding model from the consumption of fossil fuels and this is a way to do that.”

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Oregonians in the program pay 1.5 cents per-mile and are refunded any gas tax money they’ve paid.

Illinois Senate President John Cullerton proposed a road usage charge for vehicles last week as a way to pay for road maintenance in the future. He withdrew the proposed bill almost as quickly as he introduced it.

Michelle Godfrey says the “the gas tax is becoming more and more unfair,” because some cars use little or no gasoline are not paying for upkeep of the roads.

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Godfrey says Oregon will eventually phase in a mileage charge for everyone, but the Oregon legislature will be trying to decide next year how to do it. It’s unclear whether it’ll be done by vehicle model year, miles per-gallon a vehicle gets or something else. Also not determined is whether there’ll be a different charge for different kinds of vehicles.