It is possible, and it could be extremely effective, but not straight way. 1. exists concept of linear city, and exists few implementations, most known: https

It is possible, and it could be extremely effective, but not straight way. 1. exists concept of linear city, and exists few implementations, most known: https://en.wikipedia.org/wiki/Volgograd https://en.wikipedia.org/wiki/Volgograd 2. In linear city, possible to create just one line of train, and station every mile, and all other transport muscular, or something like pneumatic-mail and open conveyors. In some cases, could be effective to make rectangular network of train lines. Sure, for old cities with lot of legacy, only train transport in many cases impractical, because usually their logistic network is not linear and even not rectangular. And train largest problem, is large radius of turn. Currently in most large cities exists underground train or light city train, in different countries named tube, metro, underground.