I thought of something along very similar lines about a decade ago, and rejected the concept because of overriding safety concerns. Besides which, how do you transfer yourself and all your luggage in the short period of time allowed before the vehicles undock? Instead, I propose a system of modular cars that can travel on regular roads for local travel, and high-speed MagLev rail for longer travel. The vehicles are stationary when transferred from one mode to another, avoiding most all the safety problems. The same rail network can also be used for freight. Please, please, check out http://www.levicar.com/ for more details.