> But what about a case where someone 3 or 4 car lengths ahead makes a quick lane change and an accident occurs behind them? You'd have to be going extremely s

> But what about a case where someone 3 or 4 car lengths ahead makes a quick lane change and an accident occurs behind them? You'd have to be going extremely slowly for 3 or 4 car lengths to be a safe following distance. On a typical 60-70mph freeway you should have a gap of at least 15-20 car lengths, and then accidents like that will happen only when other factors are at play (and if those factors are predictable like water on the road then your distance/speed should be adjusted accordingly). While I think that example was bad, your point about there existing accidents without single points of blame is still valid.