These signs are not Danish, not officially at least. "Fartkontrol" is a Danish word but the sign is not an official sign and in Denmark we wouldn't split "fart" and "kontrol" into separate words.

'Fart' does refer to speed occasionally, but the key here is that it's always called 'Hastighetskontroll' in Swedish. Note the double 'L' in 'kontroll' and the compounding of 'hastighet' and 'kontroll'.

then you weren't in sweden. we dont even signpost them.

and "fart" is where you get "fare", as in to travel. or rather, we both got them from german.

It'd be more accurate to say they share the same origin. Swedish and English are both part of the Germanic language family.