It is completely possible to drive conservatively and with caution, while exceeding an arbitrary limit. Here's one for you, a 3-lane highway adjacent to a shopping centre and school. The 60km/h speed limit is too high during shopping & school hours, but stupidly low at 3am on a clear night with no traffic around. My opinion of a safe speed is very different for those 2 circumstances - I don't see how that equates to bad judgement.