Originally Posted by Kingsqueak
An interesting reason this isn't an included option on a lot of the nav systems is simply one-way streets and a liability concern if people weren't sharp enough to realize that reversing their route would send them the wrong way.
I found mention of this on some other forums and frankly it makes sense if you consider the IQ of the average citizen these days.
In a GPX file, a route is just an ordered set of waypoints, which would lead me to believe the GPS calculates the route between points, so the above shouldn't be an issue. Does garmin transmit extra info in a route?