A standee line on a bus:

Question

On a bus designed to carry standing passengers, no passengers may stand in front of the rear of the driver's seat. Any such bus must have a line on the floor, or some other marking, that indicates where passengers may not stand. This is called a standee line.

Accepted Answer

Marks where riders may not stand.

Answer

Is useful to get passengers to board and exit the bus.

Answer

Is a part of the air conditioning system.