Austin, Texas ? In what sounds like another tall tale told by a Texan, the Lone Star State has embarked on an audacious project to build superhighways so big, so complex, that they will make ordinary interstates look like cowpaths.

The Trans-Texas Corridor project, as envisioned by Republican Gov. Rick Perry in 2002, would be a 4,000-mile transportation network costing an awesome $175 billion over 50 years, financed mostly if not entirely with private money. The builders would then charge motorists tolls.

But these would not be mere highways. Proving anew that everything’s big in Texas, they would be megahighways — corridors up to a quarter-mile across, consisting of as many as six lanes for cars and four for trucks, plus railroad tracks, oil and gas pipelines, water and other utility lines, even broadband transmission cables.

Supporters say the corridors are needed to handle the expected NAFTA-driven boom in the flow of goods to and from Mexico and to enable freight haulers to bypass heavily populated urban centers on straight-shot highways that cut across the countryside.

The number of corridors and exactly where they would run have yet to be worked out. But the Texas Transportation Commission on Dec. 16 opened negotiations with the Spain-based consortium Cintra to start the first phase of the project, a $7.5 billion, 800-mile corridor that would stretch from Oklahoma to Mexico and run parallel to Interstate 35.

“Some thought the Trans-Texas Corridor was a pie-in-the-sky idea that would never see the light of day,” said Perry, who has compared his plan to the interstate highway system started during the Eisenhower administration. “We have seen the future, and it’s here today.”

But as the plan rumbles along in the fast lane, some have called it a Texas-size boondoggle. Environmentalists are worried about what it will do to the countryside. Ranchers and farmers who stand to lose their land through eminent domain are mobilizing against it. Small towns and big cities alike fear a loss of business when traffic is diverted around them.

Even the governor’s own party opposes the plan. The GOP platform drafted at last summer’s state convention rejected it because of its effect on property rights.

Perry is undeterred. “I think it will be a model for future infrastructure construction in the world,” he predicted.

Texas economist Ray Perryman said the corridors could generate about $135 billion for the state over the 50-year span and lure new industry by offering efficient shipping routes for goods and utilities. “Any time we can do something better, faster and cheaper, it’s going to give us an advantage,” he said.

The new rail lines could also lower the risk of chemical spills in urban areas, said Perry spokesman Robert Black. “We have hazardous materials running through our city centers because of a rail system that was built 100 years ago,” Black said.

For the Oklahoma-Mexico corridor, Cintra plans to spend $6 billion for about 300 miles of four-lane highway from Dallas to San Antonio and give the state an additional $1.2 billion for improvements along the route. In return, Cintra wants to operate the toll road for 50 years.

Other potential corridors could stretch east-west from Orange to El Paso, and north-south from Amarillo to Laredo.