rubbernecking delay 

n. traffic delay caused by motorists' gawking at any type of car accident, even those on the shoulder of the road. Delays caused by rubberneckers are often the main reason for the slowing of traffic after an accident, rather than the accident itself.

Sorry we're late— 95 was backed up for miles from a rubbernecking delay.

rubbernecking delay by theodorickb April 12, 2011