I just looked at the crash scene. It's a little bit weird. Looks like his car rolled UP a hill on the side of the road, on the southbound side.

The original tweet claims he was traveling northbound, which is downhill, and which makes more sense for losing control. However, it looks like he crossed the median and the car continued off the other side's road, and rolled up the hill before stopping.

Don't be fooled by the straight appearance. There are a number of small curves on the way down. It's on a moderate curve for most of the way. Look at the map.