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But how about just giving us streets with no cars?

Big roads and parking garages are so common in American cities that it's easy to forget these places once functioned exceptionally well without them. However, in their persistent battle to satisfy the demands of motorists, many urban areas are losing out.

In the early 1960s – when highway construction was at its peak and cars were just beginning to leave their mark – a handful of critics predicted there would be irreconcilable tensions between vibrant cities and their motorized inhabitants. Nearly 50 years later, researchers at the University of Pennsylvania published research validating this idea.

Their conceptual model was based on a straightforward premise: cars take up a lot of space, especially when it comes to storing them all day while their owners work.

What the researchers found is that cities that have lots of cars have fewer people. So, to achieve real density will mean building cities that are for people and not for cars. There is no way (airbags, alarms, and what have you) around this fact.