eli5: How do they decide what the speed limit is for a road?

Question

Basically the title. I’m curious what they do to decide. surely they don’t just stick a random number on a sign and call it a day.

In: 16

Answer 1

They monitor the average speed that drivers tend to travel on it based on their own sound judgement and then set the limit 25% lower than that in order to establish a revenue stream.