The Durango highway is the only road crossing the Sierra Madre Occidentales in mid-Mexico. It's a heavily travelled 2-lane road with breath-taking views, sharp corners, precipitous drop offs, and steep hills. It's a marvel of engineering - matched only by the competence and care of the hundreds of tractor-trailer drivers who daily rely on it. Not so all drivers, witness the many crosses along the way.
[One of our few frustrations on this trip was not being able to stop and take photos when we wanted.]