While we may consider the alternative fuel movement a relatively new fad, human beings have long sought alternative methods of power and transportation outside of petroleum oil. Necessity is the mother of invention after all, and during war time oil can be in short supply, leading to innovative (and often wacky) solutions like the gas bag vehicles of World War I and World War II.
During both the first and second World Wars, nations like Britain, France, and Germany sent most of their petroleum to the battlefront, leaving little for the civilians at home to use. While the U.S. enacted gas rationing and carpooling to make the most of their limited gas resources, other nations had almost no spare oil to go around. This led to the widespread adoption of alternative fuels, including natural gas created as a by product of iron production.
Because materials used to make high-pressure gas tanks were in short supply, and the tanks were more prone to explosion (especially when there were bombs dropping with regular frequency in London), compressed natural gas was a non-starter for most people. But people still needed to get around, so an alternative was filling up massive gas bags with natural gas, and strapping it to the roof of a car, truck, or bus. These huge air bags were the only way to get any sort of usable range out of this alternative fuel, and you could easily tell how much mileage was left by how deflated the bag was.
Some people actually enclosed the gas bags in the roof of the vehicle, making for a tall-but-otherwise-normal-looking vehicle. But most privately-owned vehicles just drove around with a giant bag on top of their cars, which presented a huge fire hazard at a time when just about everyone smoked cigarettes or cigars. Low bridges also presented a problem, and as you might imagine giant air bags strapped to the roof of a car aren’t very aerodynamic, meaning most gas bag vehicles drove at or below 30 mph/50 kph.
While gas bag vehicles were most popular in wartime Europe, up until the 1990s some more remote areas of China still used gas bags to power public transit. Today, gas bags have been all but supplanted by compressed natural gas, or CNG vehicles, which used high-pressure tanks to store much more gas in a much smaller area. But should the proverbial shit hit the fan, and oil is no longer a viable option for most people, gas bag vehicles could make a comeback.
But let’s hope not.
Source: Low-Tech Magazine