Would High-Speed Rail from Dallas to Houston Make Sense?

"As in the previous two posts, I focus on a mythical 240-mile-line between Houston and Dallas, which was chosen to avoid giving the impression that this back-of-the-envelope calculation represents a complete evaluation of any actual proposed route. (The Texas route will be certainly far less attractive than high-speed rail in the Northeast Corridor, but it is not inherently less reasonable than the proposed high-speed rail routes across Missouri or between Dallas and Oklahoma City.)

How big is the reduction in carbon-dioxide emissions associated with switching from cars to rail?"

Thanks to Franny Ritchie