Not familiar with how EU countries decide what speeds to put where, but if they are anything like the US, they might be referring to the fact that 30 KPH is basically what a school zone would have posted, but yeah speed limits exist for your safety and the safety of others, if it’s 30KPH, there’s probably a reason.
In the UK it was originally based on something like the 85th percentile: the speed most drivers would normally pick for the road given no imposed limit.
These days it’s more based around what politicians live where, so we have dual carriageways with central reservations, which would normally be 70mph, but because some fancy nob has a house there and doesn’t like noise, it’s got to be 40mph. They don’t say that though, they say it’s down to too many accidents in the area, or speed reduction for air quality or some other nonsense (if it was for air quality then the limit’d be 60mph due to the designed-in peak efficiency at 55mph).
school zone
Not kids = not people
Probably it was living/residential area/zone/street (see street sings). Speed limit: walking speed.
But different countries decide on different walking speed. In RUB for example it’s 20 km/h.
