Fortunately, the snake survived, and went slithering into his hidey hole in the roots of one of the huge trees that line the bike path. I used a stick to touch the end of his tail to make sure his spine wasn't broken, and he reacted in about the way you would expect a not-run-over snake to react.
Sorry this isn't a very good picture. Since T-Mobile pushed out the Android Cupcake upgrade, my phone has been ridiculously, pathetically slow. It took almost a minute and a half to get the camera application open and snap a picture. By that time, the snake had spent 30 seconds slithering around on the bike path checking itself out (which would have been an awesome shot), and then gone about 20 feet into the grass. Boo Android! Fix your shit!
The snake was about four feet long and about the width of two fingers. The head was sort of bullet-shaped, as opposed to shovel-shaped, so it's probably not a viper. My guess is garter snake.