i was travelling along a motorway some years back at 55 mph behind a lorry ,very safe a lot of you would say ,then i noticed a lorry a foot from the rear of my van ,so i pulled forward reducing my safety margin ,and he followed ,there were also lorries in the middle lane ,so i could not overtake ,so i was in a situation where i couldnt brake for fear of this lorry crashing in the back of us ,i couldnt overtake ,and all i could see in front was a lorry ,i was just praying that nobody put there brakes up ahead ,in the end i pulled over to the hard shoulder ,i have towed at the legal limit on French motorways ,but i have never been so scared as when doing 55 mph with that lorry behind us