It might just as well be some other obstacle: slow moving vehicle, car stuck on the road, end of a traffic jam. People really really need to learn that you need to be able to come to a dead stop within the distance that you can see.

I suppose it depends on the country, but usually roads mandate minimum speeds (tipically half the max speed) in order to avoid issues like this. Anything lower than the minimum speed should be treated like a static obstacle, so maximum speed should always take into account unexpected hazards.

Given that cyclists cannot tipically maintain the minimum speed required in any country road, they cannot share the road with faster vehicles. It's either curbs or segregated roads. Anything else is plain craziness.

(Yes, there are plenty of other countries, but those seem to be the two most discussed here)