Innovations like ride-hailing, self-driving cars can't fix urban transport's woes

Urban transportation is undergoing a revolution. Offerings such as Uber and Lyft, as well as car- and bike-sharing services are widely believed to reduce congestion and generally make urban dwellers more mobile; driverless cars are expected to provide further benefits. Yet the notion that these innovations always make things better is far from a given: The new services are a net good only if they complement traditional public transportation systems rather than compete with them.