<P> Jackknifing refers to the folding of an articulated vehicle i.e. one towing a trailer , such that it resembles the acute angle of a folding pocket knife . If a vehicle towing a trailer skids , the trailer can push the towing vehicle from behind until it spins the vehicle around and faces backwards . This may be caused by equipment failure , improper braking , or adverse road conditions such as an icy road surface . In extreme circumstances , a driver may attempt to jackknife the vehicle deliberately in order to halt it following brake failure . A jackknife event of a heavy vehicle can be fatal to the driver as the top of the cab can be crushed or sliced off as it swings round violently and tries to fold under the trailer . </P>
when is an articulated lorry most likely to jackknife
If a vehicle towing a trailer skids