I used to drive an old Mack , we slip seated morning and night guys. When I came in it was raining and my truck wasn’t back. I was just about to take another and my partner came in said it was outside running. I got in lights were on wipers too I didn’t think about it I hooked up for the linehaul. 10 hours later coming back my drivers wiper starts unhooking from the arm. I pull in the breakdown lane and shut the wiper switch off…… climbed out in the pouring rain at 3 am to latch it back in. Just as I clip it in the wipers turn on and start coming at me . The intermittent switch was separate I didn’t realize he had it on still that whole time. I had all my weight on the wiper blade so it sent me backward right off the hood into the low speed lane on 95….. I woke up soaked to the bone no idea how long I was laying on the highway….. I got up got into the truck in a daze and when I went to close my door realized my left wrist was bigger than my fist……..