Peter Grey wrote:

I've always wanted to know if in the days before the car, the dirt roads
were "worn in" as they are now - with two separate tracks and no wear in the
center of the road. I would expect that the roads would be more universally
worn what with horses walking in the middle of the road in between the wheel
tracks. Watching some cowboy riding down a road worn into two separate
paths has always made me a little suspicious.

I think the answer is yes. You can still
see parts of the Oregon Trail:

http://community.netidea.com/teekay/...regontrail.jpg