Texas' highway capacity hardly is keeping up with the state's population and vehicle registration growth. The Texas Department of Transportation can't do much about that, since its budget increasingly must be devoted to maintaining current highways. The main plan to address long-term highway capacity is the Trans Texas Corridor. At 4,000 miles long and 1,200 feet wide, with a 50- to 100-year timetable and a $184 billion price tag, it is the biggest and most ambitious highway project since the U.S. interstate highway system was built almost half a century ago. It also is difficult to visualize, with so many...