Maps and routing errors would likely lead to masses of deaths, an entire motorway population rather than individuals not paying attention..

Like the various "unfinished/broken bridge" deaths that have happened with Google maps involved (not saying to blame.. but certainly not innocent either) https://www.bbc.com/news/world-us-canada-66873982 https://www.bbc.com/news/articles/cly23yknjy9o

Granted having all warning signs and barricades removed by vandals seems like the more major issue there, which drivers usually do pay attention to

Well, maybe not "this easy", but if we can all agree on an extensive test suite that all autonomous cars have to follow to be allowed on the road, it'd be almost like that, without the risk of a single bug taking down all of them.