Some subsea installations also have safety zones created by statutory instrument to protect them. Vessels of all nations are required to respect them. Some, but not all, subsea safety zones are marked by light buoys on the surface, laid as close as practicable to the centre of the zone. Certain fields which are in a development phase or are currently producing oil and gas, are designated development areas. These are marked on Admiralty Charts and, though entry is not prohibited, mariners are strongly advised to keep outside.
All installations are at risk from collision by other seagoing vessels.
Installations most at risk are those situated near shipping lanes, from vessels off-course or navigating blind. All installations should be regarded as vulnerable and need the protection which striet observance of the safety zone affords. Some ships are large and could cause considerable damage to life and property if they collided at speed with an installation. Even a small fishing vessel can infliet considerable damage to an installation and the collision may result in harm to people on the installation or fishing vessel. It is advisable for fishing vessels to keep a listening watch on Channel 16 VHF when in the vicinity of an installation.