Actually, in EU countries the law explicitly says you have to drive slow enough to react to unexpected changes on the road. If you as a driver hit something or someone, you are automatically at fault because you violated that law. There is an incredibly high burden of proof required to not be at fault as a driver.
But that’s usually not an issue, because road planners are only allowed to set speed limits that are low enough that drivers can actually react to unexpected changes. Which is why e.g. the Autobahn has a separate lane for broken down vehicles and significant setbacks and green areas to both sides of the road so you can see from a long distance away if something is in the road.