CNG vehicles must pass federal crash safety standards just like any other vehicle. Statistics show that CNG vehicles are involved in less crashes that average, this is probably due to the fact that most CNG vehicles are owned by fleets which employ driver training. CNG does not explode in a crash, natural gas has a very high ignition temperature and requires the right mix of gas and oxygen. It is less likely to catch fire or explode than gasoline in a crash.
Here are some videos of extreme abuse of CNG tanks:
CNG tank in a collision: https://youtu.be/NqH_s3YC4sE
Shooting a CNG tank: https://youtu.be/irvktfQvu4M
Dynamite a CNG tank: https://youtu.be/5ZUK-HJOfvU