Why it matters: The hierarchy: which sign wins when they conflict

Guessing wrong on this hierarchy is dangerous in both directions: trusting a broken light too much while an officer is holding you back, or ignoring a roadworks controller because 'the light was green anyway'. When a traffic light is knocked out after a storm near Enschede, the hierarchy is the only thing that decides who goes first: first whoever is giving instructions on the spot, otherwise the sign, otherwise the right-hand rule.