pile-up
noun /ˈpaɪl ʌp/
  /ˈpaɪl ʌp/
 - a road accident involving several vehicles crashing into each other
- Three people died in a multiple pile-up in freezing fog.
 - A young man died in a pile-up on the M1 last night.
 - a multiple pile-up involving a minibus and five cars
 
Oxford Collocations Dictionaryadjective- multi-car
 - multiple
 - massive
 - …
 
- cause
 
- in a/the pile-up