[mnw21cam]

I cannot vote this comment up enough. There needs to be a clear view of the obstruction in order for a person or an autopilot to see it in time. This is why you get a huge long string of cones easing people out of a lane before a road work obstruction. Similarly, warning signs should be placed before a stopped vehicle obstruction - there are quite a few countries in the world where not carrying warning signs for this purpose all the time is illegal.