The technical definition of micromobility is personal transportation using "any vehicles whose gross weight is less than 500 kg" (1100 lb. or about 1/2 ton.)” This was not chosen strictly to exclude cars, but that is a de facto consequence. If cars can be built to be that weight then they would be acceptable micromobility. However I know enough about the car business to say that it’s extremely unlikely we will see <500kg cars again. Regulations conspired to inflate car performance beyond what can be considered minimal.
The last such vehicle that I could find was the Fiat 500 from 1957. The diminutive but very clever Gordon Murray T.25 comes close but it’s not quite there.
The iconic “minimalist” cars of the 20th century, the Fiat 500 and the Mini have been re-launched in the 21st century as obese caricatures of their namesakes.
However, as the Fiat showed, 500 kg is more than enough to transport four people and vastly over-capable for the average occupancy of 1.2 that is currently the case for cars. Because most of the demand will be single occupancy, I expect 90% of microvehicles on the road will weigh less than 100 kg. Allowing 500 kg accommodates the long tail of exceptional demand.
The weight correlates to the likely distances traveled where the largest (500kg) vehicles will be used for the top quintile of trip distances (up to 80 miles).