PRT's are not novel, they've been an engineering pipe dream for at least 60 years. There was a similar design effort in the 1970s in Paris that was the subject of an excellent book by Bruno Latour called Aramis
. TFA says that PRT have been previous unworkable for "a variety of reasons, including the cost of the initial systems and the difficulty of integrating them into existing cities". The Paris project got all the way to physical prototypes, built sections of track, etc., and one of Latour's conclusions is that the PRT concept is itself unworkable. It lives in an inflexible no man's land between private vehicles and mass transit: passengers can't go where they want because the system has tracks and shared "pods", and engineers can't scale it how they want because the vehicles don't have flexible open space inside to cram in more passengers during busy times. Lose-lose, all around.