Link :
http://story.news.yahoo.com/news?tmpl=story&u=/ap/20040922/ap_on_fe_st/police_crash&e=1
LONDON - Don't give up the training. Traffic snarled for miles on a highway in northern England on Wednesday after four police cars collided with each other and blocked the road, apparently during a training exercise.
Three officers suffered whiplash while another ?- who had to be cut out of his vehicle ?- was more seriously injured, although there were no immediate details.
No other vehicles were involved, and the police cars did not appear to have been on their way to help out at another accident.
"As far as we are aware only police vehicles are involved, no members of the public," a spokeswoman for Lancashire Police said. "At this stage we think the vehicles were involved in some sort of training exercise but we have yet to have that clarified."
The vehicles collided on the northbound lane of the M61 highway near Chorley in Lancashire, forcing the closure of two lanes of traffic.