The road network we look after has five tunnels on its network: Holmsdale, Hatfield, Bell Common and the east and west tunnels at Dartford.
Environmental sensors monitor air quality and ensure the tunnel is ventilated and the environment clear of potentially harmful pollutants, for example when congestion within the tunnel increases exhaust gas levels.
Strategically placed Video Accident Incident Detection (VAID) cameras carefully monitor the tunnel and identify any number of changes to normal operation, such as stationary vehicles or vehicles facing the wrong direction, smoke, pedestrians or animals and debris in the road.
Regular work includes maintenance on jet fans, lighting, gully clearing, road sweeping, wall-washing, cross passageway door checks and sign washing.
The tunnels are overseen by our control rooms at Dartford and South Mimms.