Where are you allowed to park a trailer with a permissible total mass exceeding 2 t in built-up areas regularly on sundays and public holidays and between 10 p.m. and 6 a.m.?

In built-up areas, heavier trailers (over 2 t permissible total mass) are not allowed to be parked “regularly” overnight (10 p.m. to 6 a.m.) or on Sundays/public holidays just anywhere. The idea is to protect residential and recreation areas from noise, obstruction, and the “truck-like” parking of large vehicles.

That’s why parking is allowed in places where this is typically expected and causes fewer conflicts: in industrial areas (answer 1). It’s also allowed in wholly residential areas only if the place is explicitly intended for it, meaning specially designated parking spaces (answer 2). Without such a designated space, it would not be permitted there at those times.

Recreation areas are treated as especially sensitive; even if the road seems wide enough, that does not make it allowed (answer 3 is wrong). Width is not the key rule here—the type of area and whether parking is specifically permitted is.

Rule of thumb for similar questions: for heavy trailers in towns at night/Sundays/holidays, think “industrial area yes; residential only if clearly designated; leisure/recreation areas no.”