3 seconds when under 65. 5 seconds when it's raining or I'm moving faster than posted highway speeds. It pisses people off but I'm hauling a ton of steel and plastic around, I'm not going to risk my life and everyone's around me just because some guy is late for work or can't be patient and needs to get where he's going a few seconds before me. People tend to lose the reality of the situation when driving their super fast metal explosion machines.

When I did driver's training, they recommended about 2 seconds of distance. I find it to be a reasonable distance most of the time.