Minimum road width tends to be set for use by emergency vehicles. Can't really reduce those unless you want to mandate smaller emergency vehicles. Kei-class fire trucks exist, but don't seem popular.
While European roads are far smaller than American roads their fire engines are still based on large trucks and only about 3/4 the size of US ones. Look at the examples here: https://en.m.wikipedia.org/wiki/Fire_engine
I did read of one town in the UK that bought a Kei-class truck but it was an unusual situation.
