No city in America runs on anything resembling a free-market model. But Texas' major cities are probably the closest thing, with vast improvements to their economies and living standards to show for it. Their looser land-use laws mean that housing supply grows quickly, stabilizing prices. Their lighter tax and regulatory structure helps businesses locate there and grow. And—shenanigans from the governor's office notwithstanding—their openness to immigrants means they have cheap and robust labor forces.But one market-oriented aspect little discussed is Texas' approach to transportation. The state has 25 toll roads, more than any other state. They are particularly common in Houston and Dallas,...