When the bus stops suddenly, the luggage on the roof top will fall forward due to inertia of motion. Similarly when the bus starts the luggage will fall backwards due to inertia of rest. To avoid this, any luggage kept on the roof of a bus is tied with a rope.

Tying luggage with rope on a bus, particularly on the roof, is a fundamental safety measure driven by the laws of physics and road conditions. When a bus is in motion, any unsecured item on top is subject to inertia; if the driver brakes suddenly, the luggage wants to keep moving forward, and if the bus accelerates, it stays behind. Without ropes, vibrations from the engine and bumps in the road would cause bags to slide or bounce off the roof, posing a lethal hazard to other vehicles and pedestrians. In many developing regions where this practice is common, the rope also serves as a deterrent against opportunistic theft during stops and provides structural reinforcement for overstuffed bags that might otherwise burst under their own weight. The rope effectively integrates the luggage into the mass of the vehicle, ensuring it remains "at rest" relative to the bus throughout sharp turns and high-speed travel.