The passengers on the omnibus would not be likely to be asked.
It neednt get that far because I believe that whatever the problems there may be, my learned friends would not be able to make any more sense of the mess that the safety industry, enforcers, manufacturers and standards organisations have made of this, than you or I .
Now ask the passengers on an aeroplane what they understand by an exit sign and they will point to a text only, 25mm red lettering on a white backgound in english without any graphics. In full international use and presumably understood by all?
To answer John Dragons question directly the correct/best? solution in my opinion is to place a BS5499 sign with an arrow pointing straight ahead (up) over the door and immediately having passed through the door an additional sign pointing to the right.
There are situations where sudden changes of direction can be difficult to sign in a sensible manner, especially for example where it is necessary to turn immediately having passed through a door although there is also a corridor straight ahead. Its a situation that is not well addressed by any of the current approved standards/ regulations IMO.
Personally I think I would understand the meaning of the sign as John has installed it but there is no evidence that other people would.