"Safe" is a simplification, but some practices are obviously wrong, like less than the length of two vehicles at 120 kmH. Some off-road hazard can inject itsel

"Safe" is a simplification, but some practices are obviously wrong, like less than the length of two vehicles at 120 kmH. Some off-road hazard can inject itself onto the road without notice. All vehicles would be creeping along the freeway if they wanted perfect safety from such events. That's a tricky reasoning line. Safe distance is not intended for those cases. The point is that, given a colision, it won't be propagated. About congestion, it doesn't seem a problem if you can drive fast enough to make an issue of keeping the distance. Bottlenecks come mostly from exits.