In 1930, the British government ran a lean test on double-decker buses to demonstrate their stability. This was in response to public concern that the buses were too top-heavy and could tip over if they went around a corner too quickly. To prove the buses were safe, the Ministry of Transport ran a lean test which involved driving a bus around a corner at increasing speeds until the outside wheels lifted off the ground.

The tests were a success and proved that double-decker buses were safe and stable, even at high speeds. The government then passed legislation to ensure that all new buses were built to the same standards.

This was a great example of the government taking the necessary steps to ensure public safety, and the legacy of the double-decker bus lives on today.