Motorcycles account for a further 15% of all fatalities in a typical year. Weather is often a factor. Road design is sometimes a factor, remembering several rollover crashes that ended in a body of water and no one in the vehicle surviving. Likewise ejections during fatalities due to lack of seatbelt use is also noticeable.
Once you dig into the data you see that almost every crash, at this point in history, is really a mini-story detailing the confluence of several factors that turned a basic accident into something fatal.
Also, and I only saw this once, but if you literally have a heart attack behind the wheel, you are technically a roadway fatality. The driver was 99. He just died while sitting in slow moving traffic.
Which brings me to my final point which is the rear seats in automobiles are less safe than the front seats. This is true for almost every vehicle on the road. You see _a lot_ of accidents where two 40 to 50 year old passengers are up front and two 70 to 80 year old passengers are in back. The ones up front survive. One or both passengers in the back typically die.