That reminds me very much of an accident I had several years ago.

At the time, I commuted about 12 miles from Clinton, MA to Marlborough. I'd been commuting on my '85 Raleigh Alyeska all summer. I think it may have been into the fall by the time I had the accident; it was getting dark earlier.

Long story short: I don't remember anything from leaving work that evening until I woke up in my own bed the next morning with a hospital bracelet on my wrist, still a little muddle-headed. Someone driving by found me on the side of the road in Berlin (conscious, I think, but concussed) and took me to the hospital. The hospital diagnosed a concussion and sent me home with my then-girlfriend. When my hip pain didn't go away after a couple weeks, I got x-rays and found that I'd cracked my pelvis (I lived in a 3rd floor apartment at the time).

Anyway, there were no witnesses that I know of, and I'll probably never know what happened. It's the only concussion I've ever had. I've never had seizures or blackouts. I'd left work a bit late, and was riding home in twilight, I think. Also, I think I'd donated blood at work that day, which could certainly be the cause, but I'll never know. I was in my late 30s/early 40s at the time.