| : Agree otherwise, but the vertical bar is better avoided outside *:lanes= . I don’t see how it works yet.
*:states= : I don’t understand how it works either.
*:arrow= : Already have traffic_signals:turn= , which is more clearly named. arrow= is being proposed for road_marking= . Other modes won’t have arrows, let alone the default circle is not an “arrow”.
*:fallback= : It can mean fallback when real-time / dynamic / adaptive / regional signal coordination (Urban Traffic Control) fails, to isolated controllers. Then time period preset plans or fixed-time, when actuation fails. I feel emergency:highway= is good enough, unless there’s really different traffic control features in disasters.