Argument: Natural gas vehicle fuel tanks are very strong and safe
"How Safe is Natural Gas?". About.com: - Natural gas vehicles are very safe, for not only do they have all the same standard safety equipment as conventional cars (passive restraints, air bags, head restraints and anti-lock brakes), but they are subjected to the same crash safety tests as well.
Because compressed natural gas (CNG) fuel systems operate at pressures in excess of 3000 PSI, the fuel tank and associated plumbing have to be incredibly rugged and strong enough to contain that pressure. The on-board tanks are made of steel up to one half-inch thick and often wrapped in protective reinforced fiberglass sheathing. Plus, newer tanks are constructed of polymers and composites that are stronger than steel.
Contrast this with standard gasoline and diesel tanks in regular vehicles. These tanks are usually made from stamped steel shell halves, just a few sixteenths of an inch thick, that are welded or crimped together. In the event of a traffic accident, the ability of rugged, durable CNG tanks to withstand rupture or puncture certainly exceeds that of simple stamped steel.
"Natural Gas Vehicles The Clean Way to Go with a Domestic Fuel". Washington Gas.: Is using natural gas in a vehicle safe?
Yes. First, the natural gas storage cylinders are very sturdy, a half-inch thick compared to an eighth or sixteenth of an inch for gasoline tanks. Second, natural gas is lighter than air, so even if a leak develops, the gas dissipates into the air instead of forming a spreading pool or vapor cloud on the ground, as other fuels do. Third, the combustion temperature of natural gas, 1200 degrees Fahrenheit, is higher than that of gasoline, 600 degrees Fahrenheit. An American Gas Association study reported no injuries or fatalities after more than a half billion miles driven with natural gas vehicles.