Question

why it is difficult to stad in the upper floor in the double-decker bus?

Answer 1

The height of a double decker bus is nearly double the height of a normal bus. Also there are passengers seat on the upper part of the bus. As a result the center of mass of the double decker bus lies at a higher point. Now, if some passengers stand on the upper part of the bus, there are chances that the bus might topple while turning. So, standing is not allowed (and not advisable) in double decker bus.