This 2.9-mile spur that connects Princeton, N.J. to New York and Philadelphia commuter lines is not only the shortest regularly scheduled route in the country, it's the cheapest travel deal (at 600) outside of the Staten Island Ferry. Riders like F. Scott Fitzgerald, Albert Einstein and Bill Bradley, not to mention countless Princeton students, have taken the rickety seven-minute run. There is a minor risk that the "Dinky," as it's known locally, might be held up by Princeton students on horseback. They once did just that to kidnap their dates on the way to town.