Yeah, except when a gasoline leak occurs at a wreck, it dribbles out like water usually. Compressed gas will instantly become a high pressure leak of a gas, not a liquid.
None are THAT safe, but CNG scares a fireman more than a car with gasoline.
At 3000 psi, CNG is like driving around with bombs attached to your vehicle. CNG does rise rather than hang down by the ground. CNG=!LPG. Both LPG and gasoline are kinda nasty too. Ever use gasoline as a campfire starter? Stand way back.