smash-up 
noun informal
A violent collision, especially of cars: multi-vehicle smash-ups...
- Around 12.15 am, six cars were involved in a smash-up on Caroni Bridge, where two three-car collisions occurred simultaneously.
- It's a perfectly flat and straight six-lane highway, yet it's also the recurring scene for horrifying smash-ups, for the same reasons the road to Whistler is.
- There was severe traffic congestion on Sunset Drive a few minutes before 11 pm but police officers blamed this on a four-car smash-up on the Western Main Road.