The Task

Local Aids to Navigation

Contents
Executive Summary
Introduction
3.1 For clarity and in accordance with terminology used by the International Association of Marine Aids to Navigation and Lighthouse Authorities (IALA), the systems provided by LLAs and other authorities are described as "aids to navigation (AtoN)", to differentiate their provision from the equipment carried on board ships for navigational purposes, which are referred to as navigational aids (Navaids).

3.2 A marine aid to navigation (AtoN) may be defined as a signal deliberately placed to provide mariners with information. The signal may be:
- Visual
- Sound
- Electro magnetic (radio) IALA maritime buoyage system Diagram courtesy of IALA
3.3 A station may be defined as a point on the earth’s surface defined by geographic coordinates. The following are the categories:
- Land (a fixed station accessible by land)
- Offshore (a fixed station only accessible by boat or helicopter)
- Floating (Light Vessels, Light Floats, Large Automatic Navigation Buoys, Buoys)
3.4 Several AtoN may be exhibited or transmitted from a single station and may comprise one or a number of the following AtoN:
- A Daymark and/or Topmark (including pole marker beacons, withies, perches)
- Warning Notices e.g. notice boards which may or may not be illuminated
- Leading Mark (one of at least two separate daymark structures that provide a leading line)
- Main light
- Sector light (intensified or unintensified arc of visibility and/or colour either as part of the main light or provided in addition to the main light, in which case the term subsidiary light is commonly used)
- Auxiliary light (a light of noticeable less intensity than the main light(s))
- Precision Direction Light (a light visible over a very narrow angle to indicate a direction to be followed)
- Leading Light (one of at least two lights, which are situated on at least two separate structures that provide a leading line)
- Emergency light (a light introduced upon the failure of lights, operated by a completely separate power supply, which may be of noticeable less intensity than the Main Light(s))
- Fog Signal
- Racon
- Radar Target Enhancer
- Loran C (and other radio navigation systems)
- Differential GPS Signals †
- Automatic Identification Systems (AIS) ‡
3.5 The following general assumptions are inherent in the provision of AtoN: • Reliance is not placed on a single AtoN.
- Visual AtoN will continue to be required for the foreseeable future for position fixing and for confirmation of position/orientation, looking carefully at the mix to provide the correct balance between traditional AtoN and new radionavigation systems. Overall, it is envisaged there will be a gradual reduction across the spectrum of traditional AtoN and components, which they support, as a result of improved shipboard Navaid equipment fits and the availability of alternative systems. However, it is currently envisaged that major changes are unlikely to come into effect for a number of years.
- No light need exceed 24 miles nominal range.
- Fog signals are provided for hazard warning purposes only.
- Floating aids (such as buoys and light floats) shall not be relied upon for position fixing purposes, (unless the positions of these are capable of being monitored by a Vessel Traffic Service (VTS) or other means are in place to provide a warning to the mariner that the buoy/light float is off station.
- Unlighted buoys and beacons should not be deployed in areas where there is a significant risk of vessels colliding with the AtoN station at night. (This risk can be mitigated nowadays by the fitment of low cost self-contained LED lights having a range of 1 – 2 miles, instead of the fitment of retro reflective tape).
† For the purposes of this document DGPS is classified as a local AtoN only if it is provided by a HA/LLA to enable users to fix their position within the port/harbour. It is not classified as a local AtoN if the HA/LLA provide the service for its own use in connection with pilotage, VTS or surveying.

‡ AIS, for use on AtoN, is currently under development to provide the mariner with details on AtoN status, including whether an AtoN is off station; local hydrological and meteorological data.
Statutory Provision
4.1 Merchant Shipping Act 1995 Part VIII

4.1.1 Section 195(1) of the Merchant Shipping Act (MSA) 1995 vests in the General Lighthouse Authorities the Superintendence and Management of all lighthouses buoys and beacons within their areas of responsibility, subject to certain provisions regarding AtoN in Local Lighthouse Authority (LLA) areas.

4.1.2 THLS has a duty to carry out inspections of lighthouses, buoys and beacons under LLA Management under Section 198(1).

4.1.3 Under Section 199(1) of the MSA the Corporation of Trinity House may, with the consent of the Secretary of State, direct a LLA to lay down buoys, remove or discontinue any lighthouse, buoy or beacon or make any variation to the character of any lighthouse, buoy or beacon or to its mode of exhibition, subject to the Corporation of Trinity House (TH) first having given notice of its intention to do so.

4.1.4 Under Section 199(2) a LLA shall not erect or place any lighthouse, buoy or beacon or remove or discontinue any lighthouse buoy or beacon or vary the character or mode of exhibition of any lights of any lighthouse, buoy or beacon without the consent of TH.

4.1.5 Under Sub-section 199(4), Section 199 does not apply to any local buoy or beacon placed or erected for temporary purposes. Arising from the definitions contained within the MSA 1995, this sub-section is legally taken to refer only to temporary unlighted buoys and beacons.

4.1.6 For the purpose of Part VIII of the MSA 1995 every Harbour Authority and any other existing LLA are classified as an LLA. Section 193(2) of MSA 1995 refers. However the converse is not necessarily true.

4.1.7 Under Section 202 of MSA 1995, general transfer arrangements for local lighthouses to Harbour Authorities are laid down. This Section requires TH to transfer certain local lighthouses held by them to Harbour Authorities. Such a general transfer was made in 1991/2 when this Section first appeared as Section 33 of the Ports Act 1991. Subsequent to this general transfer, individual transfers have from time to time been made under Section 34 of the former Ports Act 1991 (now S203 of the MSA 1995).

4.1.8 Under Section 204 LLAs can surrender or sell any lighthouse, buoy or beacon held by them for general navigation to TH and, subject to consent of the Secretary of State, TH may accept or purchase it.

4.2 Harbours Docks and Piers Clauses Act 1847

4.2.1 Under Section 77 of the Harbours Docks and Piers Clauses (HDPC) Act 1847 the Corporation of Trinity House (TH) can direct a Harbour Authority (HA) to lay down buoys for the guidance of vessels within the limits of the HA.

4.2.2 Under Section 78 of the HDPC Act 1847 a HA shall not erect any lighthouse or beacon or exhibit or allow to be exhibited any light, beacon or seamark without the sanction of TH and subsequently not alter that light, beacon or seamark without TH sanction. In addition, the power and description of the light, beacon or seamark may be as directed by TH and it may be discontinued or altered as directed.

4.2.3 Under Section 78 TH is able to exercise control over third party AtoN within a HA's jurisdiction. So, if an individual or a Company, other than the Harbour Authority itself, wishes to establish an AtoN within the jurisdiction of a HA, TH is still able to ensure that the AtoN meets internationally agreed standards by having the necessary powers of sanction. It should be noted that there is no exclusion within the HDPC Act 1847 for AtoN established for temporary purposes. Thus unlighted temporary third party AtoN require the sanction of THLS. In addition under this Act, the HA may, if it deems appropriate, apply for sanction to the establishment of any of its own temporary AtoN.

4.3 Other Miscellaneous Legislation

4.3.1 In addition to the MSA 1995 and the HDPC Act 1847, the Corporation of Trinity House (TH) is able to exercise control over marking of works and the establishment of AtoN by one of the following methods:
- Through DETR consulting Trinity House Lighthouse Service (THLS) on works requiring consent under Section 34 of the Coast Protection Act 1949, as amended.
- Through TH powers of direction contained within various Transport and Works Act 1992 Orders.
- Though TH powers of direction contained within local harbour legislation viz Harbour Empowerment and Harbour Revision Orders.
- Through TH powers of direction contained within private (Local) Acts of Parliament.
- Through other marine legislation such as harbour legislation relating to Fisheries Harbours, Sea Fisheries legislation etc.
Review Criteria
5.1 Legal Advice

5.1.1 Legal advice indicates that the SOLAS Convention 1974, as amended, imposes a continuing duty to assess and periodically re-assess the degree of risk and volume of traffic and the AtoN thereby required.

5.1.2 This advice stipulates that this principle seems to apply equally to the duties of the GLAs to inspect and control LLAs. When consent/sanction is first given, a view as to what is required according to the existing degree of risk and volume of traffic, as well as to the existing circumstances and available technology is formed. However, what was once perfectly adequate may, due to changes to the degree of risk and volume of traffic, no longer be appropriate. If, under these changed circumstances, a new application from the LLA was received for consent/sanction the type, level and/or standard of AtoN may well be different due to either an increase or decrease in local requirements . Legal advice is that it is not necessarily sufficient to merely perpetuate the standard of the AtoN initially consented to/sanctioned by TH, and a system of reviewing the local requirements is necessary. Whilst this is provided for within the inspection regime, it is imperative that authorities also carry out their own regular reviews of the AtoN and level of service they provide. This is a fundamental principal of any Safety Management System and is one of the requirements laid down in the Port Marine Safety Code.

5.1.3 This section contains general information for the guidance of HAs/LLAs and other authorities on AtoN reviews and highlights specific factors that should be taken into account when conducting such reviews.

5.2 Review Procedure

5.2.1 It is recommended that:
- A major review by LLAs of all their AtoN is carried out at least every 5 years. It is likely that such major reviews will be tied in with Formal Safety Assessments of the whole Port operations. Such reviews resulting in changes to the level of service/ type of AtoN need to be discussed with/consented-to by the GLAs.
- Interim reviews of specific areas and AtoN type should be conducted, as required.
- Users should be consulted on major AtoN changes.
5.3 Factors to be considered

5.3.1 Fixed stations will be used to provide a geographical reference for position fixing purposes. It is recommended that floating stations be not used for position fixing purposes unless the positions of these stations are capable of being monitored by VTS or other means are in place to provide a warning to the mariner that the buoy/ light float in question is off station. The following factors must be considered:
- The degree of risk.
- The function(s) of the station (hazard warning, waypoint/waymark).
- The importance of the station within the mix of AtoN.
- The accessibility of the station (monitoring and control, routine maintenance, casualty response).
5.4 The Degree of Risk

5.4.1 Examples of the types of hazard that should be identified and upon which data should be subsequently collected and analysed, include but are not limited to:
- Geographical Features: headlands, points, low coastlines, islands, rock outcrops, piers, quays, locks, bridges, future developments in the area.
- Hydrographical Features: shoals, sandbanks, pinnacles, depth of water and fairways (shoaling), sand waves, width of fairway, tidal/current features, harbour approaches, wrecks, stability of or frequency of change in bottom profile, dredging, state (age) of surveys.
- The Traffic: volume, size and mix of shipping (dry cargo, passenger, high speed ships, fishing, hazardous cargoes, inland waterway craft, dredging craft); the need to ensure lane discipline within Traffic Separation Schemes; areas of traffic convergence; known changes in traffic patterns; competency of crew manning vessels entering the area; traffic safety records in general.
- Weather Conditions: the frequency and direction of storms and gales, fog and other factors causing reduced visibility.
- Environmental: the number of vessels carrying hazardous cargoes, routes followed, the numbers of these vessels in the mix of traffic, crossing traffic and consequent collision risk, wind/current considerations, areas of high population density and other sensitive areas, such as Special Areas of Conservation (SACs) etc. Increasingly environmental considerations play a role when studying the available options, which are suitable from a purely navigational point of view.
- Present Traffic Management Resources: the availability and limitations of all present traffic management resources, including other AtoN, routeing measures, anchorages, pilotage, Vessel Traffic Services (including the level of service provided), ship reporting requirements, availability of tugs, local rules and recommendations.
5.4.2 Zero risk is rarely achievable unless the activity generating the risk is abandoned. Risk Assessment is nothing more than a careful examination of what could cause harm, so that an authority can weigh-up whether it has taken enough precautions or whether it should do more to prevent harm. Risk can be reduced by examining the Risk Control options available and then introducing Risk Control Measures, such as the provision of aids to navigation. By introducing such measures risk can be either reduced or minimised. Authorities should aim to reduce any risk to as low as is reasonably practicable, the ALARP concept. Risk estimation and evaluation form vital inputs to any risk assessment. At the time of publication of this document IALA is in the process of drawing up a Guideline on Risk Management specifically tailored to authorities responsible for the provision of AtoN. It is anticipated that this Guideline will be available before the end of 2001.

5.5 Function of the AtoN Station

5.5.1 A single AtoN station may perform several of the following functions:
- Marking of underwater hazards.
- Marking a low-lying coastline.
- Identifying headlands, waypoints, routes, shoals, sandbanks and wrecks.
- Provide leading marks.
- Provide a radar target.
- Provide Traffic Separation Scheme marking.
- Provide turning marks.
5.6 Importance of AtoN Stations within the Mix of AtoN

5.6.1 The importance of the AtoN components carried at a particular station are governed by the station’s relationship to the number of AtoN in a particular geographical area and their interdependence. This is commonly referred to as the mix of AtoN for a particular area.

5.7 Accessibility of the AtoN Station

5.7.1 Accessibility for routine maintenance and casualty attendance needs to be taken into consideration when deciding upon, not only the location, but also the type of AtoN deployed, its AtoN components, monitoring and control requirements and the level of availability desired. This factor is equally important for both new as well as existing stations.
Superintendence and Management
6.1 Inspection/Audit of Local AtoN

6.1.1 It is currently the policy of THLS to inspect all local AtoN within its area of operation and to carry out a seaward inspection of all AtoN on offshore structures to ensure adequate discharge of, not only its duties under Section 198(1) of the MSA 1995, but also, its responsibilities of Superintendence and Management of all AtoN under Section 195(1).

6.1.2 The manner in which THLS discharges its statutory duty in respect of local AtoN is a combination of consent to changes, audit and inspection. This includes the duty of superintendence and management to ensure that AtoN, maintained by authorities, are appropriate and meet the agreed international standards.

6.1.3 In addition, the annual inspection is just one of the ways in which TH can ensure that, due to changes in the degree of risk and volume of traffic, as well as to the existing circumstances and available technology, local AtoN originally consented/sanctioned by TH continue to adequately meet the mariners' requirements, taking into account environmental considerations and are therefore appropriate to the current circumstances. Such changes are taken into account by the Inspector of Seamarks (IOS) discussing and recommending changes to the LLA and/or TH during and/or subsequent to his visit. It also allows the Authorities the opportunity to discuss face to face, with the Inspecting Officer, all matters relating to their AtoN provision. Special one off site visits by the IOS, Directors and other staff may also be arranged from time to time, on request of the authority, to discuss particular aspects of AtoN provision and the level of service provided. This advice is available free of charge to all HAs/LLAs and other authorities involved in the provision of local AtoN, as part of the discharge of the GLAs' statutory duties.

6.1.4 Many Local Lighthouse Authorities also consider the inspection to form an important external audit element of their port quality management systems.

6.1.5 The inspection/audit of local AtoN is co-ordinated with the other GLA's ensuring continuity of standards throughout the United Kingdom and the Republic of Ireland.

6.2 Changes to the Current Regime

6.2.1 Responsibility

6.2.1.1 Under the UK Government's Port Marine Safety Code "all aids to navigation maintained by Harbour Authorities and any other existing LLAs must be maintained in accordance with the availability criteria laid down by the GLAs and must be subject to periodic review. The characteristics of these AtoN must comply with Guidelines and Recommendations laid down by the International Association of Marine Aids to Navigation and Lighthouse Authorities (IALA)". In addition, the GLAs require Harbour Authorities and any other existing LLAs to be responsible for ensuring that any third party AtoN, within their area of responsibility, are also established and maintained to the same standards.

6.2.1.2 Those responsible for local Aids to Navigation which lie outside statutory Harbour Authorities' and Local Lighthouse Authorities' areas of jurisdiction, e.g. AtoN established as a result of Coast Protection Act Consents, AtoN maintained by Government Agencies and the Ministry of Defence – to name but a few, will also be responsible for ensuring that these are established and maintained to the same standards.

6.2.1.3 A review of the future impact of the workload of the annual inspections of local AtoN was carried out during 1999. A change in trend, in percentage defects was noted during the 1998 inspection. This change reversed the former downward trend that had been in evidence since 1989 when the defect rate had been in excess of 28%. Annex 1 gives an overview of the deficiency rates and numbers of local AtoN inspected between 1990 and 2000. This change in trend, together with the manner in which local AtoN had been inspected to date, exemplified during the review the need to introduce an audit of all local AtoN on an ongoing basis, rather than the THLS's IOS making an inspection on a particular day.

6.2.1.4 It was considered that far more effective management tools for performance measurement of local AtoN would be for authorities to report on the availability statistics of their AtoN; for audits to be effected on these statistics, as well as on an authority's Casualty Response Records; and inspections of local AtoN to be carried out on an on going basis, with emphasis placed on targeting for inspection areas where improvements could be made.

6.2.1.5 The responsibility to state and accomplish Availability Targets and lay down Response Priorities for individual AtoN rests with the Harbour Authorities/Local Lighthouse Authorities. However, to ensure consistency in application of standards and seamless transition from GLA to LLA waters, guidelines have been laid down by the GLAs. These guidelines are based on IALA Guidelines.

6.2.1.6 The setting of availability targets enable:
- The means to co-ordinate all the activities concerned with the production of an aid, affecting both reliability and maintainability, i.e. decision, design, implementation and operation (including maintenance), in relation to predetermined factors and
- Objective judgement as to whether the authority responsible meets the overall availability target, and provides a performance indicator against the users' requirement.
6.2.1.7 The numerical value of availability can be used to determine the performance of the aids to navigation against the given target, set by IALA, which reflects the opinion on the importance of the AtoN.

6.2.1.8 Authorities are responsible for ensuring that they have the appropriate maintenance resources in place in order to meet the overall availability criteria laid down by the GLAs. Guidelines on matters related to maintenance of AtoN are laid down by IALA. Harbour Authorities and Local Lighthouse Authorities should encourage their users to report any casualties to aids to navigation that they may encounter to the designated officer.

6.2.1.9 The Authority responsible for the provision of local AtoN shall keep appropriate records of Availability statistics of local AtoN and Casualty Response times.

6.2.1.10 Each Authority is required to establish procedures for responding to casualties to AtoN within the timescales as laid down and applied by the GLAs. This will include notification to the UK Hydrographic Office/Coast Radio Stations and/or the issue of local broadcasts and also local Notices to Mariners for the longer term casualties, as appropriate.

6.2.1.11 The local AtoN Chain of Accountability is detailed at Annex 2.

6.2.2 Availability Targets and Casualty Response Priorities

6.2.2.1 Availability is the function of both Reliability and Casualty Response. Overall availability targets can only be met if both reliability and casualty response, for a particular AtoN component/group of components, conform to the Availability Category level determined by an authority, based on the IALA standards. Details of the relationship between Availability, Reliability and Casualty Response can be found in Annex 3.

6.2.2.2 The following IALA Availability targets are required to be adopted by Local Lighthouse Authorities and other authorities:

a Category 1 = availability = 99.8% (this equates to 17.52 hours downtime per annum)
b Category 2 = availability = 99.0% (this equates to 3.65 days downtime per annum)
c Category 3 = availability = 97.0% (this equates to 10.95 days downtime per annum

The absolute minimum level of Availability is 95.0%.

6.2.2.3 As mentioned above, the responsibility to state and accomplish these Availability targets, be they their own AtoN or third party AtoN within their jurisdiction, rests with the Harbour Authority/Local Lighthouse Authority. However, in deciding in which Category individual AtoN are to be placed, the following are required to be taken into account:
- The importance of each aid, i.e. the more important the aid the higher the target availability
- The mix of Aids to Navigation
- Degree of risk
- The accessibility of the station
- Other local conditions prevailing.
6.2.2.4 To ensure consistency in application of standards, when setting individual Availability targets Harbour Authorities/Local Lighthouse Authorities are required to use the guidelines laid down in Annex 4.

6.2.2.5 It is recommended by IALA that Availability should be calculated over no less a period than two years –with the exception of DGPS. The GLAs have opted for calculation on the basis of a three-year rolling average, so as to ensure that the calculated Availability represents long-term AtoN performance. It is this period that is required to be adopted by Harbour Authorities/Local Lighthouse Authorities and others.

6.2.2.6 IALA emphasise that these long-term availability objectives must not appear in nautical publications, as they cannot represent a commitment of lighthouse authorities (and others) towards seafarers in any particular short period. They also emphasise that by availability they mean only the operation of the equipment itself. This is sometimes referred to as broadcast or station availability. It is also emphasised by IALA that where availability of an AtoN consistently falls below 95%, then consideration should be given to the discontinuance of that AtoN to enable resources to be focused on carrying out improvements elsewhere. This may include either the deployment of alternative forms of AtoN or implementation of other risk control measures.

6.2.2.7 The responsibility to lay down Casualty Response Priorities for individual AtoN rests with the Authority. However, to ensure consistency in application the criteria laid down in Section 2 ofAnnex 4 should be used. The setting of individual AtoN Casualty Response Priorities by the Harbour Authorities/Local Lighthouse Authorities, which are for the guidance of their designated responsible officer(s), are not necessarily intended to indicate a timescale for rectification. Rather they are intended as a means of providing guidance to the designated officer on the level of response required, based on the Availability target for the AtoN/AtoN component. Casualty Response Priority levels are based on the time a failure/casualty is reported to the required mobilisation of the response.

6.2.3 Audits/Inspections

6.2.3.1 The THLS Inspector of Seamarks (IOS) will carry out scheduled on-site audits of Authorities' availability statistics and casualty response records. These scheduled on-site audits will normally be carried out annually.

6.2.3.2 The results of the periodic on-site audits of Authorities' Availability statistics and casualty response records, which may require either corrective action to be taken or consideration to be given to suggestions for improvements, will be forwarded to the Authority concerned.

6.2.3.3 Follow up audits by IOS will be carried out, as required.

6.2.3.4 As mentioned above, the AtoN within and outwith Harbour Authority and Local Lighthouse Authority areas will still be inspected by THLS on an ongoing basis. However, scrutiny of the records of Availability statistics and response times to casualties to local Aids to Navigation, will assist THLS in identifying for inspection those areas where improvements could be achieved. The IOS and/or THLS Navigation Directorate will also use these details as a basis for offering additional advice/guidance to those authorities as appropriate.

6.2.3.5 Such inspections may be either scheduled, at short notice or unannounced, depending upon the circumstances. Unannounced inspections will normally involve neither participation in the actual inspection nor provision of resurces by the authority.

6.2.4 Records and Reports

6.2.4.1 Harbour Authorities/Local Lighthouse Authorities and others who have responsibility for the provision and maintenance of local aids to navigation shall keep records of their Availability, measured against the criteria described above, the condition and performance of such AtoN. These records must contain details of the stations where the aids to navigation components have individually failed to meet the guidelines, as well as the overall performance for their area of responsibility. From these records summary quarterly reports shall be produced with statistical analysis of the overall availability performance, based on a 3 year rolling average. These summary reports are only required to detail the average availability statistics for Category 1, 2 and 3 lights, racons, fog signals, daymarks, topmarks and position. The 4th Quarter summary will, in effect, become the annual summary report and will be also produced along the same lines. The statistics contained in the annual summary report on overall availability are to be based on the Calendar Year. It will be the responsibility of the Harbour Authority/Local Lighthouse Authority and others to submit the quarterly summary reports to THLS each quarter and also submit the annual summary report by 31 January of the following year. These reports may be submitted by post to:

Director of Navigational Requirements
Navigation Directorate
Trinity House Lighthouse Service
Tower Hill
London
EC3N 4DH

Alternatively they may be submitted:
By E-Mail to user@navigation.thls.org
or By fax on 020 7480 7662

6.2.4.2 All these above records shall be made available, by the authority, to the IOS at the time of the on-site audit.

6.2.4.3 The summary reports provided by authorities, together with the results of the on-site audits and inspections undertaken by the IOS, will form the basis of a revised annual statistical report by THLS on Local Aids to Navigation that is submitted to the Secretary of State.

6.2.4.4 The results of the annual on-site audits and any follow up audits will be conveyed to the authorities on a standard proforma. These results may include corrective action requests and/or suggestions for improvement. In the case of a corrective action request and/or suggestion for improvement authorities are required to return this proforma having entered on the form details of the action they intend to take or indeed have already taken.

6.2.4.5 The manner and format in which the availability records are to be compiled and presented will be the same for each authority responsible for the provision of local AtoN. To assist in this task, and ensure consistency in reporting by authorities, it is intended that a common programme will be provided by THLS, free of charge, to all authorities responsible for 10 or more local AtoN. This programme will be accompanied by an operators' handbook/manual. THLS will have exclusive copyright of the 13 programme and it may not be copied without the express permission of THLS. This programme will operate in Microsoft Access. Programmes designed upon similar lines are also used to provide the basis of the GLAs' internal reports to their respective Boards and to DETR on their own AtoN.

6.2.5 Timescales

6.2.5.1 It is intended that audits of local AtoN availability statistics and casualty response records will commence in 2002. However, commencing with the 2000 inspections, better use of existing THLS resources has already facilitated improved efficiencies in the work of the THLS Inspector of Seamarks, as well as helped ease the burden on the provision of resources faced by some Authorities.
Aids to Navigation Characteristics
Wrecks
Policies and Procedures
Definitions
Abbreviations / Acronyms
Annexes
Annex1 – Deficiency rates and numbers of Local Aids to Navigation Inspected 1990-2000

Annex2 – Local Aids to Navigation Chain of Accountability

Annex3 – Availability, Reliability and Casualty Response
1 Availability is the function of both Reliability and Casualty Response. The Availability objective can only be met if Reliability (MTBF = Mean Time Between Failures) and Casualty Response (MTTR = Mean Time to Restore) conform to the objectives set by IALA.

2 Performance monitoring by means of numerical Availability shall thus be calculated using the formula method: calculated as:

MTBF x 100 = A(%)

------------------
MTBF + MTTR

3 For the purposes of reporting on local AtoN availability statistics where A is the Availability objective, MTBF is the mean value of the length of time between one casualty and the next casualty and MTTR is the time taken to restore a casualty measured from the time of failure/reporting of a failure to when Normal Conditions are Restored (NCR).

4 Task priority can be determined by the matrix of the importance of the aid, type of aid, resources available, and maintainability. Trinity House Lighthouse Service has adopted a failure/casualty response priority of 1 to 5, which is predetermined when the casualty is reported. However, actual time taken to reach the casualty can be influenced by time lost due to sea and weather conditions, the lack of manpower and transport resources and the distance involved.

5 In order to improve Availability to attain the target and thereby improve the performance related to the requirements of the user, a number of factors should be investigated as follows:

5.1 In the correlated equation of MTBF and MTTR, reviewing one of the possibilities below or all in combination could increase MTBF:
- Specifying better quality or environmentally more suitable equipment.
- Improve the quality of Preventative Maintenance.
- Increase equipment redundancy.
- Design for through-life maintainability.
5.2 To reduce the MTTR, the following time components need to be investigated, all of which form part of casualty response:

5.2.1 Report time; i.e. the time to report a casualty. This is affected by whether a station is monitored by the most suitable means available and, where remote control and monitoring facilities are available, whether such facilities are reliable enough to accurately respond to failure.

5.2.2 Task priority; i.e. the applicability of the Casualty Response priority level set for the station based on 2 above.

5.2.3 Time to prepare; i.e. time to alert manpower and resources and gather the necessary tools and materials to affect a repair.

5.2.4 Travel time; i.e. time taken to arrive on station, closely related to 5.2.2 and 5.2.3 above.

5.2.5 Logistics availability; i.e. the methods of transport used to attend to the casualty.

5.2.6 Time lost; i.e. due to adverse weather or sea conditions, which is related to 5.2.4 and 5.2.5 above.

5.2.7 Time to repair on site, i.e. time taken to fully restore the equipment to its published characteristics.

6 It must be borne in mind when assessing the above that only discrepancies in the published characteristics of an Aid to Navigation (casualties) should be included in the Reports. Partial system or equipment failure that does not lead to a casualty, i.e. minor and major defects covered by redundancy does not need to be included in the Reports. The exception to this being where the backup systems significantly differ from the normal characteristics of the AtoN.
Annex4 – Performance Targets and Casualty Response Priorities
1 Aids to Navigation – availablity categories

1.1 AtoN Minimum Availability Targets are based on IALA Guidelines.

1.2 Category: 1 (99.8% Availability)

1.2.1 Lights of primary navigational importance having a range of 15 nm or greater including key Direction, Leading and subsidiary lights.

1.2.2 Lights of less than 15nm range marking major hazards, waypoints or situated in areas of heavy traffic including key Direction, Leading and subsidiary lights

1.2.3 Lights fitted to buoys marking new wrecks

1.2.4 Racons

1.2.5 Position of:
- Major Floating Aids (Light Vessels, Light Floats and Lanbys)
- Buoys equipped with racons
- Buoys marking major waypoints
- Buoys marking new wrecks
- Buoys marking IMO Traffic Separation Schemes/Deep Water Routes
1.2.6 DGPS Systems used by vessels for position fixing purposes (see footnote 1)

1.3 Category: 2 (99.0% Availability)

1.3.1 Lights greater than or less than 15nm range including Direction, Leading and subsidiary lights not assessed as Category 1 stations

1.3.2 Lights fitted to buoys marking IMO Traffic Separation Schemes/Deep Water Routes

1.3.3 Cardinal buoy topmarks

1.3.4 Position of buoys marking existing wrecks and minor waypoints

1.4 Category: 3 (97% Availability)

1.4.1 Buoy lights other than Category

1.4.2 Fog Signals

1.4.3 Daymarks, including withies, pole beacons, warning notices; and topmarks, other than Category 2

1.4.4 Position of buoys other than Category 1 or 2 buoys

2 Casualty Response Priorities

2.1 Applying practical resources to Casualties to achieve the minimum availability requirements the following Casualty Response Priorities are laid down. For harbour authorities casualty response should be co-ordinated by the local Port Control/VTS Centre (which should have the availability of a duty Senior Marine Officer on a 24 hour basis for complex decisions). For other authorities this response should be co-ordinated by the relevant designated Department/Team within their organisation.

2.2 Wrecks designated as dangers to navigation have priority over all AtoN casualties

2.3 AtoN Casualties – Priorities

2.3.1 Priority 1
The highest priority (other than Wrecks). Immediate response to investigate and mobilise or divert appropriate resources, other priorities to be amended accordingly. Radio navigation warning required via Local Port Radio/Vessel Traffic Services and where appropriate via UKHO.

2.3.2 Priority 2
Urgent mobilisation of maintenance resources, subsequent to initial investigation. Radionavigation warning required (as Priority 1).

2.3.3 Priority 3
Personnel and transport response within 24 hours. Radionavigation warning required (as Priority 1).

2.3.4 Priority 4
Personnel and transport response within 48 hours. Radionavigation warning required (as Priority 1).

2.3.5 Priority 5
Required action to be determined by the Port Control/VTS Centre who are authorised to re-classify the Casualty Priority 1 – 4 if circumstances dictate. Radionavigation warning may be required (as Priority 1)

Footnote 1
For the purposes of his document DGPS is classified as a local AtoN only if it is provided by a HA/LLA to enable users to fix their position within the port/harbour. It is not classified as a local AtoN if the HA/LLA provide the service for its own use in connection wtih pilotage, VTS or surveying.

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