Example: You get on the bus at A and pay on boarding. After the bus passes B, the light sign indicates that you need to pay when getting off the bus. You only need to pay again when you get off after passing C, not before.
Some will just remember the people boarding, some will hand out the token to those getting on while the bus is in the buffer zone, some don’t really seem to care.
So the bus driver on my usual bus asked to pay while boarding in the buffer zone. They never asked for this before. Now I will have to swipe the card while alighting too. Hope I don’t get charged twice.
Some lines depending on distance will charge twice, at boarding and alighting. Else you will be charged only once by the reader. It will flash red or make a sound or both.