CHARLOTTE, N.C. -- Road construction on I-77 is set to begin next year-- this time it's for toll lanes.

Since North Carolina drivers already pay the highest gas tax in the southeast, you might wonder why the DOT is signing off on tolls.

North Carolina drivers already pay almost 38 cents for every gallon of gas, and that's just the state taxes.

So why is the state having to turn to tolls?

Because traditional taxes are flat lining as NC Transportation Secretary Tony Tata told an audience at the Chamber of Commerce earlier this summer.

"Our primary funding sources of motor fuels tax, highway use tax and DMV fees are flat-lining on us because we're hooked to the efficiency of the combustion engine," Tata said.

So more miles per gallon for means relatively fewer tax dollars for the state.

And those taxes are a part of what pays for new roads, along with highway use taxes on car sales, hit hard by the recession and DMV fees.

At the same time, new residents, older bridges and narrow roads are placing more demands on infrastructure costs.

"Any system that relies heavily on gas taxes do so at their peril," NCDOT Board Chair Ned Curran told the Chamber of Commerce.

The hard choices have divided fiscal conservatives.

Cornelius Town Commissioner Dave Gilroy describes himself "as conservative as anyone who has ever sat in office in North Mecklenburg" when it comes to tax rates.

But Gilroy would rather support a tax hike than endorse toll roads on I-77.

"I hate tolling infrastructure even more [than taxes]," Gilroy said.

The NCDOT has even floated the suggestion of a mileage fee so drivers who use roads more would pay more.

But many drivers have a visceral reaction to the notion of the state keeping track of their mileage.

To pay for future road and bridge construction, it will really be a case of pick-your-poison.

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