For those of you who have not had the pleasure of driving in Southern Mexico, let me assure you that if you have a shoulder on a carretera that you can temporarily drive on to let a faster driver pass you, an illegal act in the U.S., you had best do so even if that shoulder is narrow with occasional pedestrians and the roadway is curving. It takes a while to get used to this but driving along a roadway with a Mac Truck an inch off your rear is instructive.