When I was a college student in Pittsburgh, I walked a lot, mainly because I didn't own a car. For longer trips (say the five miles from the university to downtown), I depended on public transit (streetcars at that time in Pittsburgh). When the population had fewer cars and was more densely housed within city limits, these were reasonable practices. The spread of automobiles to the larger part of the citizenry had enormous impacts on the structure of cities and Pittsburgh was no exception.
Around a century ago, a large group of civic-minded Pittsburghers assembled committees to examine various aspects of the city ranging from parks and playgrounds to the rivers and railroads. One of their reports covered public transit. They projected the need for a subway in the downtown area to address street congestion, something that finally occurred over 60 years later with a reduced scope. They also examined the streetcar routes with the objective of spreading them over the city map as equitably as possible to place areas of highest density within a quarter mile and most areas within a half mile of public transit. They adjusted the distances to account for the hilly topography and the presence of hillside steps in many parts of the city. Only a fraction of their recommendations were ever implemented. It's interesting to contemplate what might have been in light of subsequent history.
It's also interesting to see how some of these ideas resurface in various forms. The walkable city, the overlay of bike lanes on public streets, and the new towns planned around a central commercial/business core have all been reactions to what Ax rightly points out. It's just easier to get in your car and drive. The move to electric vehicles that's afoot now is clear evidence that most people who can afford the choice are not ready to surrender their cars. The sprawl of suburbia, the ongoing widening of expressways, the space dedicated to parking lots and garages - all are witness to our devotion to the car.
The self-driving car, available at one's beck and call, might woo us away from individual car ownership, but it does nothing to eliminate car-related infrastructure. It actually increases traffic as the cars respond to orders, then make the desired trip, and finally go to either a parking place or another order.
A number of amenities ranging from local shops and businesses through public transit to delivery of parcels from stores to homes are needed to allow a comfortable life without a personal vehicle. I really don't see how these can be achieved on a large scale in our country as it is now structured. Previously unforeseen options, such as work-at-home and widespread online sales may have a bigger influence on how our lives and cities are structured.
Big Al
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Money seems to buy the most happiness when you give it away.
Why does everything have to be so complicated, all in the name of convenience. -ShiroKuro
A lifetime of experience will change a person. If it doesn't, then you're already dead inside. -MarkJ