I think my husband might have sideswiped this rat snake when he pulled down the driveway. At first I thought it was shedding it's skin, but people who are familiar with snakes tell me that this is an injury. For the moment, while waiting perhaps for someone who can help it, I've covered it with a storage container covered with a light colored sheet to protect it from the sun's heat.
Okay...a friend put me in touch with a rehabilitator who looked at the photo and said the snake was severely injured and the kindest thing to do would be to take it to a vet and have it euthanized, OR, I could cover it with a towel and then put it and the towel in a pillow case and refrigerate it for a couple of days and then put it in the freezer for a few more days, and then bury it. That sounds like a plan I can follow.
This is the time of year that these sorts of creatures are coming out of hibernation and we must be vigilant when we drive - it's not only potholes that we have to look out for.