To be fair, speed limits aren't always at all obvious.
My dh got caught in an unfamiliar, not built-up area, and had to go to court. Since it was his first ever speeding offence in over four decades, before the court appearance we drove up and down that stretch of road, looking in vain for any signs or road markings - there was not one in the direction in which he'd been caught.
In the other direction, there were easily visible signs.
At the court one of the ushers told us that he himself had been caught in that section, as had so many others, and there had been masses of complaints about the lack of signs/ markings.
If the point of speed limits is limiting speed, why no signs or road markings? It made no sense, especially when so many people had evidently been unaware of the limit and caught there.
On a subsequent trip a couple,of years of years later, signs and markings had finally appeared on that particular stretch of road, so all the complaints must have had an effect.