PHOENIX — It could soon cost more to register your vehicle in Arizona.

On a 17-13 vote Monday, the state Senate gave final approval to allowing the director of the Arizona Department of Transportation to levy a fee on each vehicle. The legislation, already approved by the House, now goes to the governor.

House Bill 2261 does not spell out how much the fee would be. Instead, it tells the agency chief to raise enough to fund the highway patrol division of the Department of Public Safety and a little bit more for good margin.

Legislative budget analysts say the amount ADOT would need to raise is $149 million. That translates to $18.06 for every vehicle, above and beyond the normal registration fee.

The measure would also result in a sharp hike in the minimal registration fee now imposed on motorists who purchase alternate fuel vehicles. Beginning in 2020, the levy will be based on the price of the vehicle, just as it is now for cars and trucks powered by fossil fuels.

The legislation — and the decision to leave the fee up to the ADOT director — is the culmination of a multi-year effort to find new money to help build new roads and repair existing ones.

That is supposed to be financed largely through the gasoline tax. But that 18-cent-a-gallon levy has not been raised since 1991 when gasoline was in the $1.20-a-gallon range.

And while there are more vehicles on the road, they also are more fuel efficient, with the number of road miles driven — and the wear and tear on the roads — increasing faster than new revenues.

What’s made matters worse is that current and former governors and lawmakers, looking to balance the budget, have siphoned off some of those gas tax revenues to pay for the highway patrol. Sen. Bob Worsley, R-Mesa, said that has left fewer dollars for both urban and rural transportation needs.

And given the unwillingness of lawmakers to hike the gas tax, Worsley said funding the highway patrol out of a fee on all vehicles using the roads seemed to be the most politically palatable.

But the method of raising the money drew catcalls from several lawmakers.

The Arizona Constitution spells out that any increase in taxes and fees can be approved by only a two-thirds vote of both the House and Senate. And that margin is not there.

So the measure crafted by Worsley along with Rep. Noel Campbell, R-Prescott, leaves the actual amount to be raised to the ADOT director. And a recent Arizona Supreme Court ruling concluded that such agency-raised fees are not subject to that two-thirds vote.

Sen. Warren Petersen, R-Gilbert, suggested to his colleagues that there’s something sneaky about that.

“Don’t kid yourselves,” he said.

“This is a tax increase.” And it should require a two-thirds vote, Petersen said. “But, unfortunately, this is a nice little loophole to get around it, a loophole that should be closed.”

He called it “the worst kind of tax increase” because the levy will be determined not by elected legislators but an official appointed by the governor.

“We’re going to tell an unelected bureaucrat to go ahead and raise these fees to whatever he wants to,” Petersen said.

What’s even worse, Petersen said, is that there is no guarantee that once the new vehicle fee funds the highway patrol that the money saved will be used for transportation needs.

“How is this happening?” he asked.

Sen. Sylvia Allen, R-Snowflake, also balked at approving a yet-to-be-determined fee.

“I just can’t in good conscience pass something I don’t know what it is exactly the amount I passed,” she said.

But Sen. Martin Quezada, D-Glendale, said the lack of specificity on how the saved dollars would be used does not bother him. In fact, he said that’s a key reason he’s supporting it.

“We’ve shown the political will here today that we can raise revenue to take care of all of the other issues,” Quezada said.

Worsley said he presumes Gov. Doug Ducey will sign the measure as the governor had made a similar proposal several years earlier, albeit with a fee of about $8.