There are plenty of ideas out there on how to bring in more transportation revenue, says Lt. Gov. Brad Little.

The hard part is finding which ones will work.

"If we don't invest money in roads and bridges, we get safety and congestion issues," said Little, chairman of the Governor's Task Force on Modernizing Transportation Funding. "We are looking at every conceivable source of revenue we can think of."

Little and his task force considered a long list of potential new funding sources for Idaho's roads and bridges last week, he said, and they might have found some answers.

At the top of the list: New fuel taxes, a sales tax on fuel and increasing vehicle registration fees.

"What surprised me was how close the committee agreed on these issues," Little said.

Other ideas, some less feasible, included fees per miles traveled, excise tax on rental cars and more toll roads.

"Now we need experts to tell us why this is or is not a good idea," he said.

The need for more sustainable transportation funding is growing critical, he said, as the current funding sources - the federal fuel tax, state fuel tax and vehicle registration fees - aren't going to be enough for long.

Between 1990 and 2007, Little said, Idaho's population shot up 50 percent. Miles traveled went up 55 percent.

Meanwhile, purchasing power of the federal gas tax has gone down 74 percent.

"As vehicles get more and more fuel efficient, we're going to have to do something," Little said, pointing out that the more fuel-efficient cars bring in less for fuel taxes.

He personally favors high registration fees or more fuel taxes over a sales tax, he said.

"If we did collect sales tax on fuel, that means if you're paying for gas at $3 a gallon, that doubles the tax today," he said.

He also likes the idea of charging for miles traveled so greener vehicles would pay an equal amount as gas guzzlers for the use of bridges and roads, he said.

Technology isn't available that could make that kind of tax possible right now, though, he said.

That could also be a problem for a fuel sales tax, he pointed out.

"There's no mechanism to collect at service stations now. They go by volume and not by dollars," he said.

Little hopes the state would incorporate new fees in ways that minimize consumer impact, he added, like increasing registration fees when fuel taxes are low.

"The state shouldn't be in the position to increase the burden on families, but we've got to do it (transportation fees) sometime," he said.

The transportation task force will make its recommendations to the Idaho Legislature in November or December, Little said.

He can't guarantee any will be implemented.

"I don't see the legislature or the governor passing any kind of fee if the economy gets worse," he said.

But he pointed out what Gov. Butch Otter had told him.

Overlooking unmet maintenance needs is the same as deficit spending, he said.

"It's the same as those other states spending money they don't have," Little said. "We have a responsibility to maintain roads and bridges."