johnsher wrote:
ok, presuming I'm completely wrong, how long does it take to overtake a 56mph hgv when you're doing 85mph?
If you don't know how to work it out, you shouldn't be participating in this debate.
Assuming truck is 50ft long, travelling at 60mph; car pulls out to overtake at 2s separation, pulls back in at 1s separation; speed differential is 30mph. Car needs to make up 176ft + 50ft + 88ft = 314ft at relative 44ft/s = ~7s. If Vectra car was also at speed differential of 30mph (115mph) and was on Sixy's tail half-way through the overtake (ignoring braking), she would made up ~200ft which would have taken ~4.5s. Therefore, Vectra may have been 4.5 x 44 = ~200ft behind at commencement of overtake. However, if Sixy pulled out at 3s separation (perfectly reasonable), she would have had to make up 289ft which would have taken ~6.5s so Vectra may have been ~290ft behind. Or Vectra may have been at 130mph in which case approximately double the above distances.
This is all academic because we weren't there. Maybe Sixy did misjudge the speed differential, maybe not. We don't know. What I know is that if I am carrying high speed on a motorway, I should be looking far enough ahead to anticipate a car overtaking a truck. If I am doing that, I will have no difficulty in losing enough speed, without drama, to allow a car ahead to complete an overtake without coming aggressively close to its rear, unless it pulls out when I'm very close and still at high speed differential. But then I'm still in the wrong because if there was any chance that could happen, I should have reduced the differential to obviate the risk.