Funny thing, I was on the highway today and saw two pieces of logs, probably fallen from a vehicle, one in my lane and the other in the RH lane. Each log measured cir. 12" long and 3" thick and were very rough shaped.
I was not far enough from the car in front of me in order to notice the log and react in any way. It was rather more like "huh, lookadat, could've hit it!"