Just watched tonight's channel 5 programme, Eddie Stobart: Trucks, Trailers and Tinsel, which was about the valiant efforts made by the drivers to deliver all the Christmas stuff in appalling weather conditions.
It was an excellent programme, but one thing made me wonder. Fiona, jackknifed on the exit slip road of a motorway, which was on an uphill slope. When they pulled her clear, she reversed back onto the motorway, to come off at another junction. Surely this would be illegal, unless there was special allowances made because of the atrocious weather.
That is indeed the definition of 'jacknifed', however if you view the last 5 mins of the programme again using the link previously posted you will see the cab doesn't deviate by more than about 15 degrees - the artic just slid sideways onto the snow covered verge.