slipways The port has extensive facilities for repairing, maintaining, drydocking and slipping of all types of vessels. Two floating drydocks are located off the west coast of Tsing Yi Island and two northeast of Lantau Island. The largest is capable of docking vessels up to . There is also a large number of smaller shipyards, which carry out repairs to vessels and build specialised craft, including sophisticated patrol craft and pleasure vessels for overseas markets. Port facilities and services Moorings and anchorages The Marine Department operates and maintains 58 mooring buoys for seagoing vessels. Of these 31 are suitable for ships up to 183 metres in length and 27 for ships up to 137 metres. There are 44 special typhoon mooring buoys to which ships can remain secured during typhoons. This improves efficiency and reduces operational costs of vessels through elimination of unnecessary movements. In addition to the three Immigration and Quarantine Anchorages designated for visiting vessels to complete port formalities, there are eight dangerous goods and eight general-purpose anchorages providing temporary berthing spaces for vessels. The areas and water depths of the anchorages are diversified to accommodate different sizes and draughts of ships calling at Hong Kong. There are over 460 modern marine aids to navigation throughout Hong Kong waters to guide mariners to and from their berths. Navigation safety All fairway buoys are lit and fitted with radar reflectors. Traffic Separation Schemes operate in the East Lamma Channel and Tathong Channel. The Marine Department's VHF radio network provides comprehensive marine communication coverage throughout the harbour and its approaches. The department has direct communication links with other maritime authorities and users worldwide. Locally, the department's Maritime Rescue Co-ordination Centre (MRCC) maintains direct contact with emergency response services, which include the Government Flying Service, Marine Police and Fire Services. MRCC provides 24-hour maritime distress alert monitoring and co-ordinates all maritime search and rescue operations within the Hong Kong search and rescue region in the South China Sea. A comprehensive vessel traffic service is provided by the department's Vessel Traffic Centre (VTC), with radar surveillance and tracking capabilities as well as a fully integrated data handling sub-system, covers 95% of Hong Kong waters used by seagoing vessels and ferries. The VTC offers advice on the activities of other vessels and gives navigational information to mariners through a sectorised VHF network. This ensures the safety standard and traffic efficiency of the port.