Germany here: we have to do the HU (Haupt Untersuchung, the german MOT) every 2 years.
The m3w is classified as vehicle class L5e (that means a vehicle with 3 wheels and quicker than 45 km/h);
in march 2024, the CO Value was (engine warm and turning 2.000 RpM, allowed between 2.000 and 3.000 RpM) 0.14 [Vol.-%], allowed is max. 0.3, so the "car" passed the test.

greetings, Achim alias Waldemar


4 aircooled cylinders, 7 tires, not waterproof: my m3w Bluebelle (2013) and my 2CV Gundel (1990)