[jws]

Most US States say two seconds. Some say three. German law requires 0.9 seconds, but studies show 41% of drivers there follow closer in relaxed conditions!†

Out here in the relaxed midwest most drivers in 60mph traffic seem to follow about 1.5 seconds.

It looks like highway planners expect to get 1900 vehicles per lane per hour at saturation, that averages 1.9 seconds between cars.

␄

† https://en.wikipedia.org/wiki/Two-second_rule (wherein it proclaims sleep impaired drivers in bad conditions should leave 6 seconds). If you think you need a six second reaction time, pull over and get out of the car.

[kbutler]

I'm curious how you've determined "most US States". I cited CA above - 3 or more, Washington wants 4 seconds above 35 mph. Florida says 4 seconds during normal weather and traffic conditions (more if hazardous). Utah does say 2 seconds. Texas wants 4 seconds above 30mph. New York said 2 seconds but "In bad weather and when following large trucks, increase the count to at least three or four seconds for additional space."

And in any case, the 2 seconds is not the "suggested follow distance" it's the legal MINIMUM. That is, "You're clearly unsafe if following at any less than this," rather than, "Close up any gaps more than this."

[qznc]

The rule of thumb in Germany is "half speedometer" which corresponds to 1.8seconds. For example, if you drive at 80km/h, keep a 40m distance. The reflector posts [0] on streets out of towns have a 50m distance, so the distance between two posts at 100km/h.

[0] https://de.wikipedia.org/wiki/Leitpfosten