Well, In Flagey, it is a one way road for exemple. No bus is going that way and i don't know if other ppl use the bus tag for something else. So Emergency tag seems suitable the Fire Dpt and not so disturbing on the map. When a road is oneway but if "oneway:bus = no", we don't tag it emergency.

It is also a good way for the Fire Dpt toinventory all the railways that are suitable for the fire engines or ambulances.