What minimum distance must you keep from a preceding vehicle if you drive a bus outside a built-up area, in a tunnel whose length exceeds 500 m?

Road Traffic Regulations precisely specify the mandatory following distances in tunnels over 500 m in length outside built-up areas. When driving a bus, the minimum distance from the vehicle ahead must be 50 metres. Maintaining this distance is crucial for ensuring safety and enabling a prompt reaction in the event of a sudden stop in traffic.