The Vuchic article on PRT contains some very faulty arguments. The first paragraph begins with the notion that the PRT idea having been around for 30 years makes it an unworthy concept.
History is rife with concepts sitting on the shelf for long periods before implementation.
Mr. Vuchic argues that only large vehicles are efficient enough to justify the system expense. It would be helpful if he could speak to what kind of efficiency he is talking about. In the simplest terms it is what people prefer. Begin with the heart of the system - automatic control. Recent studies of French systems show that even with large vehicle systems automation improves the economics.