Hay truck accident

Last Thursday we were headed to the hills to collect a load of firewood. While driving along the highway we saw this semi truck, with a trailer full of huge hay bales, tip over right in front of our eyes. We were the first one the scene of the accident. Fortunately, the driver was OK and got out of the cab. He said his tires hit some of the gravel on the side of the road and it caused him to flip over. That's the first accident I've ever actually seen happening. There were 2 other trucks of hay coming up behind him, so they stayed with the wrecked one, and we went on our way to the hills.