Operation Stack is a procedure used by Kent Police and the Port of Dover in England to park (or "stack") lorries on the M20 motorway in Kent when services across the English Channel, such as those through the Channel Tunnel or from the Port of Dover, are disrupted, for example by bad weather, industrial action, fire or derailments in the tunnel. Operation Stack is managed by Kent Police using powers under the Civil Contingencies Act 2004 and coordinated by a multi-agency group known as Operation Fennel. According to Damian Green MP, by 2007 the system had been implemented 74 times in the 20 years since it was first introduced. Causes Operation Stack is implemented whenever there is an urgent need to inhibit the flow of traffic to the Channel Tunnel and the Port of Dover, which handle 90% of freight traffic between the United Kingdom and mainland Europe. There are officially only 550 parking spaces for HGVs in Kent, so if access to cross-channel services is restricted, congestion would quickly spread across the county. The most common causes of Operation Stack are severe weather that either cancels or restricts ferry services, industrial action at the French ports of Calais, Dunkirk and Boulogne, and electrical failures in the Channel Tunnel. Procedure The M20 is the main road from the London Orbital Motorway, the M25, the world's largest and busiest ring road, to the Port of Dover, the busiest ferry terminal in Europe, and the Channel Tunnel. It runs south-east from the M25 near Swanley through Kent via the county town Maidstone, Ashford and Folkestone to Dover. Most of the road is three lanes in each direction as far Folkestone, then two lanes to Dover. Lorries are parked on the carriageways as below, with all other traffic diverted onto the A20: Phase 1: Coast-bound from Junction 11 (Hythe) to 12(Cheriton), Phase 2: Coast-bound from Junction 8 (Maidstone) to 9 (Ashford), Phase 3: London-bound from Junction 9 (Ashford) to 8 (Maidstone), Phase 4: Coast-bound from Junction 8 (Maidstone) to 12 (Cheriton), If congestion reaches from Junction 8 to Junction 11 (), traffic for the Port of Dover is diverted to Manston Airfield while traffic for the Channel Tunnel remains on the M20. By stacking lorries along the motorway, up to 3,000 additional parking spaces for freight can be created. The decision to implement each phase of the programme is taken in conjunction with