Roads are public, but cars are, for the most part, private. But what if most cars were shared by citizens. What benefits could this have on sustainability and quality of life?

For example: car pool to work in a public car, and instead of leaving it sit there all day in a dedicated parking spot, it gets used by workers running errands, or by the business itself, but back in time for your return trip home.

And since you don't own the car, there's less pressure to justify using it every day.

Chris Bradshaw is a retired municipal planning official who has been active in walking advocacy and car-sharing entrepreneurship for over 25 years. He's written a paper on how car sharing can reduce the 'drive to drive' and improve the walking environment.

I spoke to him as he prepared to present his paper at the Walk21 conference in Toronto.