CNG /LPG are safer than Petrol& Diesel.
CNG is lighter than Air – dissipates quickly in atmosphere
Have high ignition temperatures compared to Petrol & Diesel – does not ignite with engine heat..
CNG cylinders are made of robust seamless steel tubes and made to sustain high pressures upto 350 bars . Likewise LPG tanks are very tough are fitted with fool proof safety/Multivalves which evacuate fuel to atmosphere in case of impact.