AUSTIN, Tex., Dec. 31 (AP) - Texas has embarked on a project to build superhighways so large and so complex that they will make ordinary Interstates look like cowpaths. As envisioned by Gov. Rick Perry, the project, the Trans-Texas Corridor, would be a 4,000-mile transportation network costing $175 billion over 50 years and financed mostly, if not entirely, with private money. The builders would then charge motorists tolls. These 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...