Is it more dangerous to be in a passenger car with compressed natural gas than with a petrol fuel tank when it comes to rear-end collisions?
Lawrence Godwin, on eZine claims there is a explosion risk with CNG vehicles, although suggests that they are overall safer than petrol vehicles.
A NG cars' fuel tank is usually located in the vehicle's trunk area, which reduces the space available for other uses, especially for long distance trips. There is also the danger of explosions during rear end collisions. Overall, CNG vehicles are considered to be safer than gasoline powered vehicles.
Further Info:
The Clean Vehicle Education Foundation don't address the rear-end risks, but suggest that, overall, CNG is safer than petrol.
The Cutting Through the Fog blog speculates that a ruptured CNG tank is safer than a ruptured petrol tank.