On UK red London buses, it says that standing or on the top deck or stairs while the bus is moving is prohibited due to physics and is actually illegal.
I have noticed myself that the top deck can get very shaky and you could fall easily.
I usually like sitting on the top deck for long bus journeys.
How does one get off the bus when sitting on the top deck safely but also not making the bus driver/passengers wait?
As someone who lives in London and uses the buses I have never thought that the prohibition on standing on the upper deck precludes leaving your seat in anticipation of getting off the bus - you're not standing, you're walking! Indeed if boarding the bus it is quite usual still to be climbing the stairs when the bus has left the stop, you have no option but to walk upstairs to your seat.
My practice is to aim to be at the bottom of the stairs by the time the bus reaches the stop where I get off. Pragmatically, if you delay until the bus stops you're likely to be obstructed by eager boarding passengers.
You're absolutely right that one needs to proceed with caution; it can be bumpy, and the bus movements are amplified by being upstairs.
If your bus stop is relatively popular (quite a few passengers get off) then there is no need to worry.
You can start getting off when other passengers start going down the stairs. Additionally, people will probably want to board the bus as well so you can disembark the bus when other passengers get on.
If the bus stop isn’t popular it is probably be a request stop meaning the bus only stops there upon request.
You could push the stop button and begin going down the stairs when the bus starts stopping or a better option is to go down the stairs a few stops before/the stop before when the bus stops so you are already on the bottom deck.
