Inside his generally routine budget proposal Wednesday, Gov. Gary Herbert included a challenge to dramatically overhaul the state’s tax structure, a call echoed by The Salt Lake Chamber the next day.

The governor floated a series of ideas — things like trashing special tax loopholes, collecting online sales tax, and taxing e-cigarettes.

But there was one proposal that would impact every driver on Utah’s roads: Replacing the current gas tax with a per-mile fee to fund Utah road construction and maintenance.

The reason, Herbert says, is cars are more efficient, and there are more hybrid, natural gas and electric vehicles on the road that burn less — if any — gasoline. That means they aren't paying for the wear and tear they put on the road.

“They’re burning up the roads … and the road doesn’t know if it’s an electric powered car or gasoline car,” Herbert says. “If we’re transitioning to electric cars and don’t collect a tax in some way, then they get a pass on [paying for] the roads they’re beating up the same way as a gas-powered car.”

The Utah Department of Transportation is in the early stages of planning a small pilot project to test the notion of charging drivers by the mile. Chances are they'll find results similar to those in Oregon, which ran two pilot programs and launched OreGo in 2015, the nation’s first road-use fee program.

Conceptually, requiring drivers to pay to use the roads and not gasoline makes sense, but there are drawbacks that have to be addressed.

The biggest hiccup is how to track miles traveled. Going strictly by odometer readings doesn’t capture the family vacation to California or road trip to Colorado. In Oregon, cars were equipped with sensors that monitor the miles driven, which works, except when it doesn’t. It turns out Oregon had problems with the gadgets not working right in some cars or being disabled by drivers.

And Utahns may not be thrilled with the notion of the government mandating they install a device to track when and where they drive. Oregon said it dealt with the privacy concerns by not tracking precise locations and not retaining any specific data.

I’m sure that will make the black helicopter crowd feel better.

And how should the state deal with the big rigs that crisscross the state, pounding the pavement and paying their share of gas taxes? Oregon left the gas tax in place and then refunded drivers what they paid in gas tax, based on the data from the monitors.

But outfitting the roughly million cars in Utah with monitors, collecting the gas tax, then refunding money to those drivers becomes an administrative nightmare, not to mention very, very expensive.

The biggest problem with the per-mile pricing, however, is that it moves us in the wrong direction when it comes to trying to reduce tailpipe emissions and clean up our air.

We know that 57 percent of pollution comes from vehicle tailpipes and, to try to reduce the emissions, the state has been trying to incentivize the purchase of electric, natural gas or hybrid vehicles, even giving tax credits for the purchase.

I drive a hybrid, meaning I get mocked relentlessly by my friends and fellow motorists, but I also get good mileage and don’t pollute as much. So does it make sense to charge a hybrid driver the same amount to travel a mile as the jumbo SUV that burns three times as much gasoline and belches three times the pollution over the same distance?

In the Oregon pilot project, drivers of the least efficient cars and trucks ended up getting a big break when they paid by the mile instead of by the gallon, while those driving the most efficient cars saw a big increase.

That doesn’t make much sense, and moves us away from our clean air goals.

A possible solution could be to create a tiered-price structure. Instead of everyone paying 1.5 cents per mile, for example, gas guzzlers could pay more — say 3 cents — while moderately efficient cars pay 2 cents and the most efficient pay 1 cent per mile. Those who need to drive a truck for work — a contractor, for example — could get a waiver to pay the lower rate.

The flexible pricing also has another potential benefit: The state could charge more for miles traveled during rush hour — perhaps twice as much — collecting money when cars are stuck on the highway just burning gas and discouraging drivers from being on the road in peak times.

Or, there could be a premium charged for driving on red air days, or clogging up the overcrowded canyons on the way to the ski resorts.

If it’s done right, the per-mile road use fee that Herbert and the Legislature are contemplating is an intriguing idea that could provide a more reliable, equitable funding stream than our current gas tax.