High Speed Rail Sweet-Spot

This article on Slate discusses a recent, fictional map of high-speed rail in the US by Alfred Twu that has rejuvenated discussion on the topic. The most interesting point to me, though, was this:

Experts who study light rail often mention a “sweet spot” of between 100 and 600 miles for high-speed rail corridor trips. Shorter than 100 miles, and a rider is more likely to want to take a conventional train, a car, or a bus. Longer than 600 miles and a rider is better off flying.