There's an irony to the national ribbons of concrete created by President Eisenhower in the 1950s that link the lower 48 states.

"Interstates were built as 'free ways,'" the assistant chief engineer for the Wyoming Department of Transportation said Wednesday in Casper.

But they're not, Pat Collins said.

The $6.4 billion cost of just maintaining Interstate 80 - not counting any new construction - will grow to the point that it will consume the state's entire highway budget in a decade or two, he said.

The 13,000 vehicles - about 19,500 in the Rock Springs-Green River area - that cruise I-80 from Nebraska to Utah will more than double in the next three decades, with truck traffic increasing at a faster rate than cars.

By 2015, half of I-80 will need major rehabilitation or replacement.

The federal funding won't keep pace to maintain Wyoming's interstates 80, 25 and 90, even though Wyoming receives about 80 percent of that highway money from Washington, compared to other states that receive about 50 percent, said Tim McDowell, WYDOT's programming engineer.

So the Legislature authorized WYDOT to study the concept of making I-80 a toll road.

"The fact that it's even brought up shows we've got an issue," he said. "Transportation is the lifeblood of Wyoming."

Collins, McDowell, and Nick Amrhein from infrastructure consulting firm Parson Brinkerhoff presented the depressing data about the highway's future to a couple dozen legislators, citizens and truckers. Today, they will speak at 5 p.m. at the Best Western Towers West in Gillette.

"This is a study to generate information for the (Joint Transportation, Highways and Military Affairs Interim) Committee Amrhein said.

During the study, they've researched the possibility of setting up noncash tolling points, either midway along the highway or at Cheyenne and Evanston, to capture the large number of trucks that use I-80 as the main upper U.S. freight corridor across the country.

The technology has improved to the point where cameras could identify license plates and charge drivers through credit cards or other methods, Amrhein said.

But some issues remain, such as whether the federal government, which created the freeway system, will allow states to set tolls.

Some people at the meeting objected to the idea, saying that truckers already pay more proportionally than passenger vehicles for using highways.

Sheila Foertsch of the Wyoming Trucking Association said her organization favored the study because all options to pay for the road should be considered.

But the WTA opposes a toll system on existing highways, she said, adding that Wyoming should cover some of the costs through higher fuel taxes, Foertsch said.

The federal government also needs to fulfill its obligations to supply highway funding for rural states, she said.

Reach Tom Morton at (307) 266-0592, or at tom.morton@trib.com. Read his blog at tribtown.trib.com/TomMorton/blog.