Personal Rapid Transit Will Never Happen
"PRT is a dream of combining the convenience of the automobile with the mass production of transit. Four-passenger cars would run on fixed guideways elevated above the ground that would blanket an urban area on a grid. You go to a station that is no more than a couple of blocks from your home, get on the next empty car, punch in your destination, and the computer-controlled car will whisk you there at 70 miles per hour... We already have a personal-rapid transit system. It is called the automobile. The cost of building a parallel system will be huge, and until that system covers an entire urban area, few people will use it."
Thanks to Chris Steins