What's the minimum distance you should maintain from the vehicle in front of you when you get stucked in a traffic jam in a tunnel?

In accordance with the Road Traffic Act, if a vehicle stops in a tunnel due to traffic conditions, such as the traffic jam shown in the picture, the driver is required to maintain a distance of at least 5 metres from the preceding vehicle. This regulation is intended to ensure there is sufficient space to manoeuvre and to facilitate a possible evacuation or access for emergency services in an emergency.