Probably Denmark then. European route E47 goes from Germany to Sweden, E55 from Greece to Sweden. In Denmark they share the same physical road for a while.
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'.
I know this is old, but it is a bit irksome that this post is titled "Fact of the day" when it can't even keep its facts straight about which country does what.
Those signs aren't from Sweden. Our traffic agency (who prints the signs) doesn't use 'fart' meaning 'speed' - except for 'gångfartsområde', 'walking speed area', which disappointingly enough doesn't even have the text on it - but mainly uses 'hastighet' meaning 'velocity'. Other commenters in this thread have posted examples of 'fart' in a different meaning being used on Swedish traffic signs.
As a native speaker of a language that's unlike anything, I envy you folks so much. Knowing enough English and German you just look at it, and go 'aaah, speediness' (I guess the 'hast'/'hastig' bit is the same as 'haste'/'hasty' in English, and the 'het' is the same as 'heit' /~ness'/ in German).
You wouldn't guess the word, but reading it in context is so much easier.
"fart" is colloquial swedish for speed, but it's not used on signs like that. as mentioned previously the correct word is "hastighetskontroll", but we don't actually have signs like that for permanent speed cameras. those signs are blue, and just depict a camera.
when "fart" appears on signs, the actual meaning is akin to "travel" or "fare", like german "fahr-" words. so we have "sjöfart" (seafaring), "rymdfart" (space travel), "fartvind" (wind rushing by when moving quickly), "uppfart" (driveway) and, importantly for signs, "utfart" and "infart" (exit and entry for vehicles).
my favorite of this is a sign nearby on a narrow road that warns about multiple exits with no sight lines.
I have to say, I normally find the "ha-ha, this word sounds like something else in English" stuff to be a bit... provincial, but I'll admit some are a bit .