I’m with VicW on this. The 2sec rule is only an approximation to the minimum following distance and has a number of assumptions (eg that the lead vehicle is going to slow progressively so the following vehicle has time to react). In fact, the stopping distance exceeds the 2 sec gap: eg at 50mph, a 2 sec gap is 147 feet, whereas the stopping ( ie thinking plus braking) distance is 175 feet. So if the truck brakes progressively and you react quickly you should be OK, but if it hits something and stops suddenly, or drops something onto the road, then provided you have sh*t-hot reactions, a dry road, good tyres, and everything else in your favour, you’re still going to hit the obstruction. Personally I prefer better odds and less stress whilst driving, the fuel saving isn’t worth it.