Question

why it is advised to tie any luggage kept on the roof of a bus with a rope​

Answer 1

We should tie the luggage kept on the bus roof because when bus moves the luggage may fall down as the bus vibrates so we should tie it with the roof.

Answer 2

we have to tie those luggage with rope because when the bus starts up due to the vibration,the luggage looses the grip and may fall off.