It's a convenient little invention but "the fact that there wasn't a simple way to know which side of a vehicle the gas tank was located on" is not quite true.
Usually, if the vehicle is of Japanese or British origin, the cap is on the left, otherwise it is on the right.
Source: I’ve driven dozens of different vehicle models all over Europe for decades. This rule always worked well enough for me.
Usually, if the vehicle is of Japanese or British origin, the cap is on the left, otherwise it is on the right.
Source: I’ve driven dozens of different vehicle models all over Europe for decades. This rule always worked well enough for me.