“The greatest environmental gains from population density arise once destinations become so close to one another that people elect to get around all by themselves - the urban-transit equivalent of the point at which a nuclear chain reaction becomes self-sustaining.” EnvironmentalismUrban DesignTransit Book:Green Metropolis: Why Living Smaller, Living Closer, and Driving Less are the Keys to Sustainability Source: Green Metropolis: Why Living Smaller, Living Closer, and Driving Less are the Keys to Sustainability