Structures asset management plan

The South Tyneside highway and infrastructure network represents the single most valuable asset for which the Council has responsibility. The network comprises almost 600km of roads, approximately 1100km of footways and cycle ways and over 100 highway structures (bridges, subways, retaining walls and culverts).

The network is used daily by the majority of businesses, residents and visitors and is fundamental to the economic, social and environmental wellbeing of our borough. It helps to shape the character and quality of the local area and makes an important contribution to wider Council priorities, including regeneration, social inclusion, community safety, education and health.

The Council recognises that it is crucial that the local highway network is well maintained; a view shared by business, residents and other highway users, who see this as a high priority area of work. This Structures Asset Management Plan (SAMP), in conjunction with the Highway Asset Management Plan (HAMP) sets out our approach to maintaining our highway assets in order to provide the best possible service to all road users.

At the heart of the plan there are two fundamental drivers:

• The application of good asset management processes to maintain the network in the most efficient and cost effective way
• A commitment to engage with our residents and other highway users with a view to achieving a level of service that meets their expectations

During the current challenging economic climate it is more important than ever to maintain our roads and other highway assets in the most efficient way and this Highway Asset Management Plan will help us to achieve our vision to provide a transport system and highway network that supports South Tyneside’s economy, safely connecting people and co-ordinating businesses within the region.

Councillor Iain Malcolm Leader of the Council

In 2009 the Council introduced its first 5 year Highway Asset Management Plan (referred to hereafter as the HAMP). The production of a HAMP is considered best practice and is also a government expectation. It identifies the optimal allocation of resources for the management, operation, preservation and enhancement of the highway infrastructure to meet the needs of current and future customers.

South Tyneside’s SAMP forms part of a suite of documents for the Council to manage the highway network in the most efficient way. Good information is the cornerstone of an effective asset management plan. If we know the asset we can maintain it and extend its life.

During the last few years the Council’s highway engineering team have continued to gather the data required to build up a detailed picture of the overall highway asset and also developed the ICT systems required to support the SAMP and HAMP.

Asset management has been widely accepted by central and local government as a means to deliver a more efficient and effective approach to management of highway infrastructure assets through longer term planning, ensuring that standards are defined and achievable for available budgets.

This Structures Asset Management Plan (SAMP) complements the Highways Asset Management Plan and gives explicit detail of how the objectives set out in the HAMP and the requirements of the Well- Managed Highway Infrastructure: A Code of Practice 2016 will be delivered in respect of the highway structures asset.

This plan contains a set of actions appropriate to current practice. Working with partners and neighbouring authorities we will continue to develop more efficient ways of working and seek to deliver continuous improvement, subject to the financial constraints that affect us all.

South Tyneside Council has recently invested in ‘Bridgestation’ as a complete asset management tool for bridges and highway structures. This system allows “what if” scenarios to be investigated and the optimum solution to be identified.

BridgeStation brings together asset management, performance management and prioritisation functions, and has the facility to bring together scanned images from other archiving systems.

BridgeStation uses nationally agreed modules for the following: -

• Inventory Management - Centrally collate detailed information on the bridges and structures inventory.
• Document Management - Store photographs, documents and drawings against an individual structure, inspection or element.
• Assessment Results - All assessment results of structures are stored in BridgeStation.
• Inspection Records - Each element can be recorded with details of its individual defects.
• Bridge Condition Values - BridgeStation calculates scores and indices automatically and reports back the latest stock condition.
• Asset Valuation - Calculate Gross and Depreciated Replacement Costs based upon the latest guidance.
• Maintenance Prioritisation - Build up prioritised workbanks of outstanding maintenance.
• Life Cycle Planning - The Life Cycle Planner module allows the creation of 60-year deterioration models for structures based upon inspected elements in BridgeStation.
• Structures Asset Management Toolkit - Analyse what-if scenarios to support proposed maintenance funding levels. Ensure performance targets are met.
• Hazard Inventory - Provides a record of the identified hazards associated with a structure.
• Environmental Assessments - Provides a record of the surroundings for a structure including vegetation, bird and protected species habitat, activity and accessibility.
• Restrictions - Stores details of any restrictions imposed on structures.
• GIS Mapping - Link directly to GIS information relating to a particular structure and displays its details, including BCI scores, information of any restrictions, etc., on a Map within BridgeStation.

This section will set out a number of aims and objectives specific to highway structures, those policies and documents that contribute to this are listed below:

• National Bridge Rehabilitation Programme
• Publication and implementation of the revised code of practice "Well Managed Highway Infrastructure (2016) recommendations.
• The introduction of Whole of Government Accounting (WGA).
• Publication of the HMEP “Highway Infrastructure Asset Management Guidance”
• Changes to LTP Maintenance Capital Block allocation from 2015/16 including the “Incentive Formula” which links highway funding to the introduction and implementation of Highway Asset Management Practice through the introduction of an annual self-assessment questionnaire.
• Introduction of the “Challenge Fund” for major/significant highway projects

The overarching aim for the highway and transport assets can be considered as the provision of a fully integrated, safe, reliable and sustainable network of transport assets, which recognises the need to cater for all modes of transportation in a modern and dynamic society without acting to the detriment of future users. Working towards this definition with the introduction of effective asset management strategies will ensure compliance with the policies and other documents referenced above.

Specific aims in respect of the management of the transport assets are:

• Network Safety
• Network Serviceability
• Network Sustainability

With the exception of the National Bridge Rehabilitation Programme, all of the above are general overarching documents which do not include any specificity for highway structures. The asset management planning process requires these overarching policies to be translated into performance targets for individual asset groups. In the case of highway structures, this has historically meant that the main priority has been the strengthening of structures that have a deficient assessed live load capacity, and has not taken bridge element condition into consideration.

Levels of service are defined as the means by which the performance of an asset is communicated to all stakeholders including highway users.

The desired condition of a structures asset is not currently defined by any specific standard, the only hard data available that can be collated and related to a structures performance relates to the condition and the assessed live load capacity (ALLC) of each structure in the asset group. In addition, the number of structures within the asset group that fall below required standards and require the implementation of interim measures could be considered.

Bridge condition is reported in accordance with the ADEPT Bridge Condition Indicator system, the condition scores are presented as average and critical values. The average value is calculated from the range of scores for each element of a structure, the critical score relates, as the name suggests, to critical elements only. Two performance indicators will be used, BCI Critical (BCICRIT) BCI Average (BCIAV), with a third performance indicator relative to the ALLC.

The BCI system features a structure condition index, for condition based performance indicators, the percentage ranges detailed for classifications ‘Very Good’, ‘Good’, ‘Fair’, ‘Poor’ and ‘Very Poor’ will be utilised. Percentage ranges relative to ALLC will be determined in consultation with neighbouring high``way authorities, and adapted to suit the STC network.

Current levels of service with regard to the three performance indicators are given below:

Figure 2 above indicates that values for all structure types lie within the 81 to 88 range, advising that a good level of service is being achieved.

Figure 3 shows values in the range of 60 to 89, showing varying performance between asset sub groups ranging from poor to good, with bridges and retaining walls in the poor category, giving cause for concern.

Assessed Live Load Capacity

Of the 32 highway bridges owned and maintained by South Tyneside Council, currently there are five known highway structures that fall below the required 40 tonne capacity, those being Albert Road (Dead Load Only), Hebburn Station Road (17 tonnes), Hedworth Village (7.5 tonnes), Hylton Grove (signed 2.5tonnes) and West Park Road (3 tonnes). This results in a Good level of service for this performance indicator. It should be remembered however, that the bridge ALLC values are based upon the results of an earlier Bridge Rehabilitation Programme, much of which requires substantiation. The performance level achieved may require adjusting based upon the outcome of this procedure.

Performance targets that can be achieved within forecast available budgets should be determined in order to gradually improve the condition of the structures stock overall, this is discussed in greater detail in Section 6.0.

BridgeStation has the functionality to forecast the level of expenditure required in order to achieve a certain condition, which in turn reflects the level of service. A number of different scenarios can be examined, these can be related to historic and future budget allocations, and will forecast spend required to maintain a particular standard. This should be undertaken as part of the lifecycle planning process. Given that South Tyneside Councils covers a relatively small geographic area with a resultant responsibility for few structures when compared with those covering a larger area, it is recommended that in the first instance, individual lifecycle plans be prepared for all highway bridges, in accordance with the recommendations of the STC Structures Lifecycle Plan.

Five policies relative to highway structures asset management are recommended:

• Highway Structures Inspection Policy
• Bridge Design Standards Policy
• Bridge Strengthening Prioritisation Policy
• Bridge Maintenance Prioritisation Policy
• Management of Sub-Standard Structures Policy

A programme of General Inspections has been implemented this should be extended to Principal Inspections. The requirements for special inspections should also be included as detailed within the STC Structures Lifecycle Plan. This procedure should be formalised into a policy document for approval. The additional policies identified above should be developed and implemented moving forward.

Asset inventory, condition and performance data provide the basic inputs to the Asset Management planning process. It is therefore imperative that this data is complete, accurate and is stored such that it can be manipulated easily.

The inventory data is divided into asset sub groups which are contained within the bridge management system. During 2016 South Tyneside Council adopted BridgeStation as their bridge management system. Until the adoption of this system, records were stored in a mixture of electronic databases and as such there are significant gaps in the available data. Highway bridges, footbridges, underpasses and culverts were input into the system first with retaining and other structures to follow. Retaining structures have been input into the system and incorporated into the General Inspection Programme during the financial year 2019 to 2020.

Asset sub groups that are, or will be included in the Bridge Management System are shown in Table 1 that follows:

South Tyneside Council is responsible for the maintenance and upkeep of 116 structures, broken down as follows:

• 32 No Highway Bridges
• 12 No Highway Culverts
• 38 No Footbridges
• 4 No Subways
• 30 No Retaining Walls

A full asset inventory for structures owned and maintained by South Tyneside Council is given in Appendix A. It should be noted that there are a significant number of additional structures that impact on the highway network that are managed by others. These structures are also included within the structures management system. Details of these structures can also be found in Appendix A of this document.

Points of contact have been established and maintained with other authorities who own and have maintenance responsibility for structures that form part of, or could impact upon, the South Tyneside highway network. Regular structures liaison meetings are held in order to gain an understanding of any proposals regarding third party structures, such that any implications for the highway network can be effectively managed.

It is fortunate that within the boundaries of South Tyneside, there is confidence that all third party highway bridges are subject to appropriate inspection regimes since they are owned and maintained by responsible authorities. Therefore no additional inspection measures are required to mitigate such a risk.

Third party consent may also be required when undertaking inspection and maintenance to STC structures, since land that lies outside of the highway boundary may be required to secure access. Prior to taking access, consent should be obtained from adjacent land owners, should consent not be forthcoming, STC as the Highway Authority, may invoke statutory powers enshrined within the Highways Act in order to gain access.

Formal access agreements are often required, for instance when a highway structure spans an operational railway. The situation in South Tyneside is complicated by the fact that several structures are jointly owned be Network Rail and Nexus (Tyne and Wear Metro operating authority). Access to trackside elements of such bridges requires consent from both parties, with separate applications and conditions applied to each. It is imperative that any inspection or maintenance programme takes this into account, as often there is a lengthy lead in time to process applications for track access and railway possessions.

For structures such as Hylton Grove and Cut Throat Dene which straddle an administrative border, in this case with Sunderland City Council, a maintenance agreement will be required such that a single authority has responsibility for maintaining the complete structure. In the case of the aforementioned, STC have taken responsibility for both bridges. This arrangement should be formalised into a maintenance agreement to avoid any potential future liability disputes.

Desired Condition

It is recommended that a two stage approach should be used for translating strategic goals and objectives and desired Levels of Service into performance targets. Firstly they should be translated into broad statements that relate to the stock of highway structures. Taking account of the detail and discussion contained so far in this document identifies the following broad statements relating to desired performance:

1. Improve the overall condition of highway structures.
2. Reduce the backlog of maintenance work on highway structures.
3. Reduce the risk to highway users from substandard structures.

Future network demand and stakeholder expectations should be accounted for when defining the strategic objectives and Levels of Service. The performance targets for highway structures should be derived from, and be consistent with, the strategic objectives, Levels of Service and the specific future demands for highway structures. These performance targets will provide the focus for the Asset Management Planning Process and allow better targeting of investment on highway structures to contribute to the delivery of the authority’s long term goals.

The following performance targets will be explored and developed..

• To improve the average condition of the bridges assets to a target of 90.
• To improve the condition of bridges assets so that all bridges have an individual BCI Critical condition of Good or better (80 minimum).
• To ensure that all sub standard bridges (prior to strengthening / replacement) are managed in accordance with BD 79.

Similar indicators will be required for both Retaining Walls and Footbridges. All performance indicators will require review as more data is collected and the accuracy of both present evaluations and future predictions increases.

Performance Data

The data held for the proposed performance indicators relates to BCIAV, and BCICRIT .An information gap analysis will be carried out for the assessed live load capacity.

BridgeStation keeps records of all inspection information to allow the condition history of each element to be reviewed. When elements are replaced or repaired the condition score is updated and this is used for the lifecycle planning toolkit allowing users to identify the value and long term planning of maintenance works.

Current Performance

Performance measurement is a process through which the effectiveness of an Asset Management Regime can be determined. It also allows the evaluation of how the assets are currently performing. Performance measurement is acknowledged as a fundamental and central component of effective asset management planning, monitoring, review and continual improvement.

Taking into account the information currently held pertaining to performance there are two main areas for consideration:

• Condition
• Assessed Capacity

Other areas for consideration with regard to current performance are:

• Management of Sub Standard Structures
• Maintenance
• Bridge Strengthening
• Parapet Performance

BridgeStation allows various methods of performance monitoring;

• Overall condition BCI average and critical scores
• Individual component condition
• Levels of sub-standard structures
• Assessment programme performance
• Inspection programme performance
• Asset Value before and after work
• Recording of sub-standard elements (Parapets etc) for replacement programming

In addition to the above, Availability and Reliability performance indicators should be developed.

Condition

BridgeStation keeps records of all inspection information to allow the condition history of each element to be reviewed at any time, also, when elements are replaced or repaired the condition score is updated and this is used for the lifecycle planning toolkit allowing users to identify the value and long term planning of maintenance works.

Table 7 gives an interpretation of the BCI score values and is extracted from the addendum to the County Surveyors Society (now ADEPT) Guidance note Volume 3.

Assessed Capacity

Knowledge of the assessed live load capacity (ALLC) of a highway structure is fundamental in managing the risk to highway users as a result of continued unrestricted use of structures that have an ALLC less that that required to accommodate all vehicles legally permitted to use the UK’s highway network. The ALLC is determined through a procedure of rigorous assessment; the assessment output will determine the ability of a structure to carry the appropriate loadings.

As part of an earlier implemented fifteen year Bridge Rehabilitation Programme (BRP), 41 (38 STC) structures were assessed, with those identified as understrength subject to strengthening works to achieve the required standard. The outcome of this programme being that of the 41 structures assessed, all were either strengthened to achieve 40 tonnes assessed live load capacity, or were subject to the imposition of appropriate weight restriction orders.

Full guidance can be found in BD101/11 ‘Structural Review and Assessment of Highway Structures’ and the review should be undertaken in accordance with the requirements detailed in this standard.

The results of each review shall be recorded in the format given in BD101/11 Annex B – Record of Structural Review Form.

The Review should be considered an on-going process, with future reviews implemented as required. The structural review and assessment can be triggered by a range of factors including changes in condition observed in inspections, proposed changes in use, changes in loading regime or abnormal loading.

Table 8 below gives brief details of the outcome of the earlier BRP.

The programme of Structural Reviews will establish the validity of current ALLC data and identify which structures require further assessment. An assessment programme shall then be implemented. All results will be recorded in the Bridge Management System. All assessments shall be undertaken in accordance with the latest revisions to the applicable design standards. The assessment process shall be in accordance with the requirements of CS 454 ‘Assessment of Highway Bridges and Structures’ and with the process set out in Section C.5.7 of the ‘Code of Practice for Well Managed Highway Infrastructure’.

In the assessment process, an important factor that can have a considerable impact on the assessment result is the surface category of the road which is categorised as ‘poor’ or ‘good’, the surface category allows the dynamic effects of transient traffic loadings passing over the structure to be estimated. A surface category of ‘poor’ should be assumed unless the road carried by the structure can be expected to be well maintained for the residual life of the structure.

Assessment information shall be conveyed in a detailed assessment report, the report shall be prepared and presented in accordance with BD101/11 Annex C – Typical Assessment Report Format. A copy of the full report shall be stored within BridgeStation with a summary of the assessment results included in the Structure Summary Sheet.

Abnormal Loads

Assessment for the effects of abnormal loads on bridges and other highway structures should be carried out in accordance with BD86/11 ‘The Assessment of Highway Bridges for the Effects of Special Types General Order (STGO) and Special Order (SO) Vehicles’. This standard is based upon a series of “SV” loading models which more closely model the behaviour of real heavy vehicles than the old HB model, and defines how a Reserve Factor should be calculated for each acceptable vehicle.

Critical Structures

A structure that has a load bearing capacity below those of others on a particular section of road is termed a ‘critical structure’. This is a technical term unrelated to the HIAMG definition of ‘critical infrastructure’. If the load bearing capacity of a critical structure is below that required for unrestricted normal traffic (typically the 40 tonne Assessment Loading defined in CS424), it will effectively restrict the whole section of the road to this weight limit. Alternatively, a structure may be critical with respect to the movement of abnormal loads. In either case, it is useful to record additional information from the assessment to aid consideration of what vehicles should or should not be allowed to use the road.

The additional information detailed below, where available shall be input into BridgeStation BMS:

• details and load bearing capacities of all potentially critical elements with live load capacities up to 15% higher than the governing element/capacity;
• load ratings in terms of HB units and all relevant Reserve Factors against SV vehicles as defined in BD 86 The Assessment of Highway Bridges for the Effects of Special Types General Order (STGO) and Special Order (SO) Vehicles;
• if practicable, lane influence lines for critical effects together with the associated limiting load bearing capacities; and
• for arches, details of the bogie configurations considered and their associated maximum axle loads.

Management of Sub Standard Structures

The categorisation of substandard structures in this context applies to bridges with a span of 1.5m or greater that carry highways for which South Tyneside Council are responsible. A gap analysis is being undertaken to determine the number of substandard structures that exist on the STC highway network.

Once Substandard, or any Provisionally Substandard Structures are identified, then they should be managed in accordance with the principles set out in standard BD79/13 ‘The Management of Substandard Highway Structures’.

A Substandard Structure is defined as a structure that is unable to meet the loading requirements detailed in standard CS 454 ‘Assessment of Highway Bridges and Structures’, A structure can also be deemed to be substandard by other means such as scour, impact damage or structural deterioration.

A Provisionally Substandard Structure is defined as a structure that has been deemed to be substandard without undertaking an assessment, or a structure that has been assessed to have a substandard capacity during any stage of an assessment, regardless of whether it is deemed appropriate to progress the assessment further.

A substandard structure does not necessarily present an immediate risk to highway users, substandard elements and potential modes of failure are identified as part of the assessment process, this information is then used to inform the requirements of an appropriate risk based interim measures regime.

An interim measures policy recognises that management of substandard and provisionally substandard structures is required since it is not realistic to implement strengthening or replacement in a short timeframe. Budgetary constraints also need to be taken into consideration, whilst a risk based analysis will allow prioritisation of the structures which present the greatest risk to highway users. The introduction of an interim measures procedure will ensure that any risk is effectively managed whilst ensuring available funding is targeted where it will realise most benefit. It is often the case that effective management will prolong the service life of a structure until such time as works can be undertaken to remove any restriction and return the structure to an appropriate capacity.

Interim measures involve the introduction of actions that will assist in risk management whilst allowing certain structures to continue to function as part of the highway network. Depending upon the nature of any defect identified, and the structural type, it may be appropriate to monitor a structure. Additional measures that could be considered include the introduction of weight and/or speed restrictions. Where structures are deemed to present a high risk, immediate closure may require consideration.

Maintenance

There is currently no established preventative maintenance programme for highway structures due to a historical lack of revenue allocation.

Structures schemes have been developed on an ad-hoc basis and have primarily been driven by aspirations to improve highway capacity.

The lack of a defined prioritisation system has resulted in maintenance works only being carried out on a reactive basis where it has been considered essential to either maintain the integrity of the structure or the safety of highway users. This short-term policy in conjunction with historical under funding has led to deterioration of structures which has allowed a backlog of maintenance to build up.

The current maintenance backlog represents capital works that have developed due to a lack of available budget that has arisen due to the increased pressures from elsewhere on revenue funding, which has historically meant a progressive reduction in bridge maintenance budgets. Any maintenance undertaken is based upon a reactive process, since there is very little resource to undertake any routine preventative maintenance.

Current financial regulations prevent the capitalisation of routine preventative maintenance. If revenue funding is not forthcoming then no preventative maintenance can be undertaken. Ultimately the situation will deteriorate until a significant maintenance intervention is required. This maintenance work can now be capitalised as it either improves functionality or improves safety. This situation does not permit routine preventative maintenance to be carried out; the situation has to be left to develop into a much more serious problem that ultimately requires several orders of magnitude greater capital expenditure than if preventative revenue works had been undertaken initially.

Parapet Performance

A strategy for review of existing parapets is required in order to identify and address any parapets that do not comply with current standards and present a high risk to highway users. Priority ranking should take into account the following factors:

1. The nature of the risk associated with the bridge in question which may be sub-divided into the following hazard groups:-
   1. Features below or adjacent to the structure.
   2. Type of highway carried by the structure.
   3. The road geometry and structure layout.
   4. Containment features
2. The degree of shortfall in the containment capacity of the parapet.

Any priority ranking procedure should satisfy the requirements of Interim Advice Note IAN97/07 ‘Assessment and Upgrading of Existing Vehicle Parapets’. The priority ranking system can then be used to inform a programme of renewal. This information can be stored in the bridge management system.

Future Demand

The performance demands placed on the highway network can be subject to change for a variety of reasons. These may include changes in population, changing traffic volumes, increasing vehicle loads and use of alternative modes of transport. Other effects on demand may also result from changes in stakeholder expectations or indeed from the highway authorities own aspirations. Any changes in the demands placed upon the highway network may affect the management requirements for a given structure. Potential areas for change in demand are discussed below:

• Vehicle Weight – any changes in permissible vehicle or axle weights will have significant implications at a national level at as such is considered unlikely.
• Vehicle Height and Width – as with vehicle weight it is considered unlikely that any changes in allowable vehicle dimensions will be forthcoming.
• Traffic Volume - needs to take into account potential future developments and their effect on the network.
• Stakeholder Expectations – stakeholder perception is often predisposed to carriageway condition and as such, an increase in performance for structures assets would give little perceived benefit to highway users, since there is often no differentiation in perception between roadworks for general highway or structures improvements, all are simply conceived to be roadworks.
• South Tyneside Council Aspirations – apart from those areas relating to performance targets there are a number of aspirations aligned to the transport strategic goals and objectives that will have an effect on the management of some structures. These primarily relate to the requirements to increase social inclusion and to promote travel by public transport. The biggest impact of these requirements will be with regard to the management of any affected substandard structures. The priority will be to avoid significant adverse effects and also to avoid restrictions that would impact upon public transport. It is important this must be achieved without increasing the level of risk that highway users would be exposed to. Detailed consultations will be required on a structure-by-structure basis.

Network Resilience

Failure of a structures asset, although relatively infrequent, can have catastrophic consequences including loss of life. Any failure will also have major implications for network resilience since repair or replacement will be a long drawn out process. Failure of an asset can be associated with many factors; however, by far the most common is as a result of an extreme weather event. These events are becoming more frequent as a result of climatic uncertainty and it is possible that the effects of a future extreme event could have implications for highway structures assets in South Tyneside. Of particular concern are those assets that span watercourses that may be susceptible to scour.

Less likely, but also of concern are the potential results of a vandalism, terrorism or accidental fire incident. An assessment of those structures that could be affected by such events should be undertaken. This will identify high risk sites and allow suitable mitigation measures to be implemented to manage any potential network implications.

Performance Gaps

There remains a significant amount of data to collect and evaluate.

The tables below present performance gaps that have been identified, and in the case of those presented in Table 9, addressed.

Lifecycle Planning

Performance gaps that have been identified will be addressed as part of the lifecycle planning process. Lifecycle planning requirements for highway structures are identified in the South Tyneside Council Structures Lifecycle Plan for Highway Bridges, Footbridges and Retaining Walls. South Tyneside Council is currently implementing procedures and recommendations in accordance with those detailed in the plan. A copy of the plan is included at Appendix B of this document.

The lifecycle plan details the long term strategy for managing the asset groups in order to attain the required performance

The fundamental requirement of lifecycle and asset management planning is the collation and retention of information regarding the condition of the existing structures stock. This information is collated through the Highway Structures Inspection Programme, now managed utilising the Bridge Station Bridge Management System.

An effective inspection regime is essential to providing key condition data, against which performance can be measured and future predictions can be made. Therefore a new inspection regime and associated processes have been developed and are currently being implemented. Such is the importance of this issue that a detailed description of the new regime is included below to demonstrate that any previous shortfalls have been addressed.

Purpose of Inspections

The overall purpose of undertaking routine inspections is to check that the highway structures stock is safe for use and fit for purpose and to provide the data required to support the good management practice identified in the Code of Practice for Well Managed Highways. Routine inspections are used to:

• Provide data on the current condition, performance and environment of a structure, e.g. severity and extent of defects, material strength and loading.
• Inform analyses, assessments and processes, e.g. change in condition, cause of deterioration, rate of deterioration, maintenance requirements, effectiveness of maintenance and structural capacity.
• Compile, verify and maintain inventory data.
• Provide suitably current data for calculating the Condition Performance Indicator (Bridge Condition Indicators).

Inspection Regime

The inspection regime should enable any defects that may cause an unacceptable safety or serviceability risk or a serious maintenance requirement to be detected in good time in order to safeguard the public and the structure and implement remedial actions. Should any defects be detected that present an imminent safety risk, the bridge inspector undertaking the inspection shall notify the Senior Structures Engineer who will then review and make an assessment of what measures are required in order to manage the safety risk. The inspection regime consists of a combination of various inspections as detailed below:

Routine Surveillance

All highway structures should be subjected to Routine Surveillance as part of regular Highway Safety Inspections. In addition members of the public have the facility, through the Council’s Contact Centre, to report any highway structure defects that they feel may pose a risk to public safety.

General Inspection

General inspections are to be carried at intervals not exceeding 24 months from the previous General or Principal Inspection. Should a structure be subject to a rapid deterioration in condition, consideration should be given to increasing the inspection frequency. The revised frequency should be such that any safety issue resulting from accelerated deterioration is detected in good time, allowing appropriate action to be undertaken. Where the deterioration results in a structure gradually approaching a state of unserviceability, a management plan should be implemented. The plan should give details of the frequency of inspections, trigger points and any action to be taken once trigger points are reached. Guidance on General Inspections for Highway Structures is included in CSS Bridge Condition Indicators Volume 2: Guidance note on Bridge Inspection Reporting and Addendum to CSS Bridge Condition Indicators Volume 2.

General inspections comprise a visual examination of all parts of the structure that can be inspected without the need for special access or traffic management arrangements. The structure and its environs are also examined for evidence of stability problems and scour. The General Inspection will also be used to verify the principal inventory data held for the structure. Table 11 shows the General Inspection regime implemented as a fundamental component of the asset management process.

Principal Inspection

Principal inspections should be carried out at intervals not exceeding six years from the previous Principal inspection unless a risk assessment has been carried out to determine an alternative interval or inspection regime. Full guidance on the Principal Inspection of structures is contained within BD 63/17 Inspection of Highway Structures. Interim Advice Note 171/12 Risk Based Principal Inspection Intervals sets out the requirements and guidance for implementing a risk based approach to determining appropriate Principal Inspection intervals and should be read in conjunction with BD63/17.

Risk assessments shall be undertaken in accordance with the recommendations given ion IAN 171/12. Once this exercise is completed, the information will be utilised to inform a programme of Principal Inspections.

Principal Inspections comprise a close examination, within touching distance, of all accessible parts of the structure, including where relevant, underwater diving inspections. Suitable access and traffic management arrangements are made to enable access to be gained to all parts of the structure.

The Principal Inspection may include a limited programme of testing such as delamination, half-cell potential, chloride and metal thickness surveys when considered necessary.

The Principal Inspection will be of sufficient scope and quality to determine:

• The condition of all parts of the structure.
• The extent of any significant change or deterioration since the last Principal Inspection.
• Any information relevant to the stability of the structure.

In addition the Principal Inspection will establish:

• The scope and urgency of any remedial or other actions required before the next inspection.
• The need for a Special Inspection and/or additional investigations.
• The accuracy of the detailed inventory data held for the structure.

Special Inspection

There are occasions when a more specific inspection, concentrating on the condition of particular parts of a structure is required. The need for a Special Inspection normally arises due to specific circumstances or following certain events, for example:

• When a particular problem is determined during an earlier inspection of the structure or similar structures.
• Following a bridge strike or road traffic accident.
• Following flood or high river flow to check for scour or other damage.
• Inspections on sub-standard structures required as a result of the management of substandard structures in accordance with BD 79/13.
• To check specific concerns following the release of new information on material durability or structural performance.
• On particular structural types or forms, e.g. metal thickness surveys on weathering steel subject to continual wetting.

Further guidance on Special Inspections is provided in BD 63/17 Inspection of Highway Structures.

Special inspections shall be instigated and undertaken by bridge inspection staff whenever the need arises, either as a result of an incident, or should any technical advances generate a need to review certain structural elements or structure types.

Inspection for Assessment

Prior to undertaking a structural assessment (or review of an existing assessment) it may be necessary to undertake an Inspection for Assessment. CS 454/01 ‘Assessment of Highway Structures’ provides all the necessary guidance required. The need for the inspection will be determined as part of the assessment or assessment review process.

The requirement to undertake an Inspection for Assessment will be reviewed on a structure by structure basis as an integral component of the proposed programme of structural reviews.

Safety Inspection

A Safety Inspection may be required following Routine Surveillance or after Information has been received which indicates that the structure may be damaged. The Safety Inspection will determine the extent of the defect or damage and whether any immediate precautions or action should be taken. This may lead to requirement for a Special Inspection.

As with Special Inspections, a specific programme for Safety Inspections is not warranted, the requirement will be based upon specific needs with inspections undertaken on a reactive basis, taking into account any accident or incident that demonstrates any potential consequences for a structures asset.

Handover, Acceptance or Transfer Inspection

Any of these inspections shall comprise a Principal or General Inspection (dependent upon the type of structure) as detailed above. They will normally be required for one of the following reasons:

• Prior to the opening to traffic of a new structure.
• Prior to the expiry of the defects correction period for a new structure.
• Prior to a changeover in responsibility for the operation, maintenance and safety of a structure from one party to another.

Again, this type of inspection will be undertaken on a needs basis.

Inspections of Sub-Standard Structures

These inspections are undertaken as a form of monitoring exercise to ensure that continued use of a substandard structure does not present an unacceptable risk to highways users. They are normally carried out at higher frequencies than General Inspection and full Guidance can be found in BD 79/13 the Management of Sub-Standard Highway Structures. These inspections, although scheduled, are managed through the substandard structure processes and are therefore excluded from the scheduled inspection regime.

Monitoring

Monitoring is the periodic, or continuous, measurement of structural behaviour by visual and/or electronic means, or other means to record data on deterioration and performance, such as deflections, strains, rotation and crack sizes. There are many instances where measurements can usefully be repeated periodically, or in rare circumstances taken continuously, so that condition and performance can be monitored over time.

It is not envisaged that the any structures asset that forms part of the highway network will require, or benefit from the introduction of monitoring techniques. Should the need arise in the future, any requirement will be clearly defined, with techniques employed that are applicable to the monitoring required. Any system of monitoring should comprise the simplest form that will generate the required data. A full appraisal of external factors that may influence the monitoring regime should be established in order that the system can be designed to take these factors into account. Any monitoring system that is considered shall comply with Section C.5.3. of the Code of Practice for Well Managed Highway Infrastructure 2016.

Value Management

Value management is a process used to prioritise the identified needs compiled in the structures workbank. Value management will provide a formalised approach for assessing the benefits of a certain action and the associated risk of inaction.

In order to determine network benefits of one scheme when compared with another a method of prioritisation is required. A tried and tested methodology is set out below.

Priority Ranking for Sub Standard Structures

The priority ranking for a substandard structure is to be calculated from the summation of three factors:

• Traffic Sensitivity
• Risk Assessment
• Maintenance Assessment

The primary priority ranking assessment is made with regard to traffic sensitivity. The most important criterion is to minimise the impairment to the functionality of the highway network from potential restrictions due to substandard structures.

The secondary priority ranking assessment (to differentiate between structures with a similar traffic sensitivity ranking) is made with regard to an assessment of the safety implications of deferring works. It could be argued that safety should be the most important criteria and should be given a higher priority than traffic sensitivity. However, it must be remembered that the management of risk in relation to sub-standard structures is implicitly accounted for by the strict compliance with BD 79/13 “The Management of Sub-standard Highway Structures”. Compliance with BD 79/13 and the adoption of appropriate interim measures will ensure that the highway network is not exposed to unacceptable levels of risk. Therefore the consideration of risk does not become a primary concern for the prioritisation of works. However, should a degree of non-compliance with BD 79 be present due to external influences then this can be accounted for in the priority rankings.

The tertiary priority ranking assessment (to differentiate between structures with similar traffic sensitivity and safety rankings) is made with regard to the extent of maintenance (strengthening) works required. Those structures requiring significant maintenance will be given priority over those requiring lesser works. This could be viewed as a simplistic measure of prioritisation with regard to residual life.

The ranking system has been configured such that for the majority of structures the predominant ranking will be derived from the Traffic Sensitivity Ranking. The Risk Assessment Ranking will provide a secondary ranking unless a significant risk is present (or the structure is not Traffic Sensitive) in which case it will become predominant. The Maintenance Assessment Ranking is to provide only a tertiary ranking and will not become predominant unless the structure is of very low Traffic Sensitivity and also has a low Risk Assessment.

The ranking system includes an exponential effect for those structures that have the following features:

• Very low assessed live load capacity.
• Lengthy, unsuitable or no available diversion.
• No (or non BD 79 compliant) interim measures.

The net effect will be to produce significantly higher scores for those structures with the highest priority. In addition these structures will have a reasonable spread of scores to allow prioritisation between individual structures.

Commonly there are a number of other criteria that can be used for the prioritisation of replacement and strengthening of Highway Structures that have not been used in the above mechanism. Examples of these would be:

• The views of the community.
• The consequences of permanent restrictions or interim measures.
• Likely rate of deterioration.
• Effect on public services due to restrictions.
• Negotiations with private owners.

These criteria have not been included, as they would have already been considered during the completion of the Interim Measures Proforma for the Management of Sub-standard Highway Structures in accordance with BD 79.

Compliance with BD 79 will not allow the lessening or waiving of an interim measures restriction purely on the grounds that the restriction may result in an adverse effect on the network, community or services provided. Should external influences be brought to bear then the risk will increase commensurately and the prioritisation mechanism will reflect this in the overall priority ranking for the structure. However, an increased priority for strengthening or replacement does not result in a lowering of the exposure to risk.

• Traffic Sensitivity

The traffic sensitivity priority ranking is to be calculated as the product of two factors:

TRAFFIC SENSITIVITY = ROUTE SIGNIFICANCE × TRAFFIC DISRUPTION

• Route Significance

Route Significance is a combined measure of the strategic importance of a route and the redundancy of the route within the immediate highway network:

ROUTE SIGNIFICANCE = HGV FLOW + (DIVERSION STANDARD × LENGTH)

• HGV Flow

This score is based upon the average daily flow of HGVs (including any other heavy traffic, ie construction plant etc.) on the Route. Where the route is subject to significant seasonal variation in traffic flows, the highest flows shall be used. In many cases actual figures may not be available but the general figures for the road classification may be used. If the road is of significant importance to local (or nearby) industry / business or is an important tourist route then the score shall be increased to the next highest category subject to a maximum of 10. (NOTE: If the route is determined to be of significant importance in the overall prioritisation of structures then actual HGV flows may need to be measured). In specific situations where the existing road classification does not accurately reflect usage then the score may be increased further subject to discussions with the Network Management Officers and agreement with the Highways and Infrastructure Manager but may not exceed a maximum of 10.

Option identification requires the implementation of good asset management principles in order to prioritise maintenance works whilst ensuring funds are targeted in a way that effectively manages risk to highway users, provides value for money and also ensures that network priority is maintained. The options that are normally considered during this process are discussed in this section.

Routine Maintenance

Routine maintenance is the regular ongoing day-to-day work that comprises servicing rather than repair and is necessary to keep the Highway Structures in operational condition, this also covers the reactive or ad-hoc repair or renewal of small elements or components which have become unserviceable due to general wear and tear or have deteriorated for other reasons.

All maintenance treatments should be designed in accordance with current standards. Care should be exercised to ensure that the latest revision of a design standard is referenced. In circumstances where a lesser standard is to be used, this should be agreed with the Technical Approval Authority and fully documented within the Approval In Principle document for future reference. The application of a lesser standard should not compromise the capacity or complicate future maintenance activity.

Renewal or Replacement

Renewal or replacement work is major planned capital work that does not increase the asset’s designed capacity, but restores, rehabilitates, replaces or renews an existing asset to its original capacity.

All Renewal or Replacement of structural assets should be designed in accordance with current standards. Care should be exercised to ensure that the latest revision of a design standard is referenced. In circumstances where a lesser standard is to be used, a ‘Departure from Standard’ will be required; this should be agreed with the Technical Approval Authority and fully documented within the Approval In Principle document for future reference.

The procedures governing Departures from Standard are detailed within BD2/12 Technical Approval of Highway Structures.

Upgrading

The growth of the asset is largely to meet increased traffic follow in new road works and housing development schemes. Upon significant maintenance and integrated transport schemes, the opportunity should be taken to review the carriageway and carry out necessary works which may include bridge widening and/or bridge strengthening works. Again, all structural proposals shall be designed in accordance with current standards.

Acquisition

Creation or Acquisition is a major work that creates a new asset that did not previously exist. If necessary the asset transfer may occur from development schemes, in which case they are adopted through a formal process. Any structure that impacts upon the highway network (regardless of whether it will be maintainable by the highway authority), or new structure associated with a development that will be adopted by the highway authority will be subject to full Technical Approval procedures. Developers should be made aware of the requirements at the earliest opportunity in order to promote liaison, avoid unnecessary delay and any potentially abortive works.

Disposal

Disposal is an activity that removes a decommissioned asset, including sale, demolition or relocation. Although disposal of ta Highway Structure asset is unusual there may be (or have been) instances where this applies.

Technical Approval Procedures

Any design or assessment work associated with maintenance, repair, or the provision of a new highway structure shall be subject to a full technical approval process which should be based upon the requirements set out in BD2/12 Technical Approval of Highway Structures. The Technical Approval Authority (TAA) shall be a Chartered Structures or Civil Engineer registered with the Engineering Council. The TAA shall have the competence and experience required to fulfil the requirements of the role.

Statutory Undertakers

Highway structures often provide a means for statutory undertakers’ equipment to cross obstacles such as watercourses and railways. Any proposed works to a structures asset must take into account apparatus present. Up to date information regarding services and their location should be sought in the early stages of any project such that appropriate measures can be planned to protect or divert services as necessary.

Specific obligations are placed upon Statutory Undertakers to ensure that for works affecting highway structures, the relevant bridge authority is consulted.

A register of streets which feature a structure that may be particularly susceptible to careless excavation should be prepared; streets identified should be given this designation to ensure any risk to the structures integrity from utility works is managed effectively. Highway Authorities and Utilities Committee Advice Note No 2009/07 gives guidance on the implementation of SED’s

Demand Management

Demand Management requires future traffic flows to be forecast in order to ensure that network usage is compatible with the assets forming the infrastructure. With respect to the structures asset, this will predominantly be managed through the development of individual lifecycle plans. The lifecycle planning process will cater for any future development proposals that, for instance, may necessitate the replacement or widening of an existing structure to meet increased demand requirements. Lifecycle planning will accommodate these scenarios, and allow structures assets to be managed accordingly, even if this results In a managed decline prior to replacement, thus ensuring appropriate resource allocation. This in itself will ensure that issues and risks relating to asset capacity are introduced into the demand and asset management process.

Target and Standard Management

Following the introduction the required Performance Indicators and close monitoring of the Levels of Service, performance gaps will be re-addressed and if it is proven that some services have been over supplied then appropriate budget and resources may be transferred to lesser performing services.

Establishment of Budgets

Capital budgets comprise two separate elements, needs based funding and incentive based funding. The former represents the guaranteed capital allowance, whilst the latter is based upon an assessment of how an authority is performing. Local authorities who have implemented asset management procedures that satisfy the requirements of the Highways Maintenance Efficiency Programme whilst demonstrating that they are delivering value for money qualify for enhanced levels of funding. Three bands of funding allocation can be granted based upon an authority’s current performance

The implications of a lower assessed band will inevitably result in deterioration of the asset stock condition, since less funding will be available across the network, as such the importance of complying with the requirements for a Band 3 assessment cannot be understated.

Prioritisation Ranking for Structures Schemes.

Capital structures maintenance schemes require a system of prioritisation in order to ensure that works are carried out in an appropriate sequence. A method for priority ranking proposed projects is set out in the matrix below:

Maintenance Prioritisation Weighting

The issues described in the matrix are scored according to severity, ‘no issue’, ‘slight issue’, ‘some issue’ and ‘significant issue’ are scored 0, 1, 4 and 10 respectively. The scores are then weighted as detailed below:

Once items within the Structures Workbank have been scored, a validation exercise should be undertaken in order to ensure the weightings described give results appropriate to the network. A sensitivity analysis may be required in order to ensure that representative weightings are being applied.

The risks associated with any structure becoming unserviceable and reducing current levels of service are:

• Network discontinuities
• Reduced mobility
• Adverse effect on economic activities
• Adverse effect on social activities
• Adverse effect on STC’s reputation

Should a structure asset deteriorate to such an extent that it requires a closure; the resultant implications have long term effects. A significant budget allocation would also be required in order to return the asset to a suitable condition and/or capacity to allow it to be reopened.

Implementation of the asset management plan forms an essential component in the effective management of the structures asset portfolio. This will assist in demonstrating compliance with the Code of Practice for Well Managed Highway Infrastructure. Details of how the integration of this plan satisfies the requirements of the code of practice are given in Appendix C of this document.

Progress made to date with the adoption of an effective bridge management system has demonstrated that South Tyneside Council have made significant strides in the introduction of an advanced asset management process, however, there is still considerable work required to ensure full implementation.

The single most important action required involves establishing the extent of the knowledge gap and instigating steps to address the issue. Once this information is available it will allow the progressive implementation of the plan, including the introduction of an interim measures regime to manage any substandard structures, until such time as works can be implemented to strengthen or repair such that the required capacities can be achieved.

A programme of review is required to establish the extent of further assessment work required, once this is established, an assessment programme should be implemented at the earliest opportunity.

In summary, the following procedures are recommended in order to facilitate compliance:

1. Initiate a programme of structural reviews in accordance with the requirements of BD101/11
2. Depending upon the result of the reviews, instigate a risk based assessment programme.
3. To supplement the General Inspection Programme, introduce a new Principal Inspection regime with the inspection interval determined on a risk based approach in accordance with the requirements set out in BD 63/17 Inspection of Highway Structures and Interim Advice Note 171/12 Risk Based Principal Inspection Intervals.
4. Initiate a review of existing bridge parapets in order to manage any risk presented by substandard parapets to highway users.
5. Initiate a review of assets that may be susceptible to damage resulting from extreme weather events, particular reference should be made to any structure that spans a watercourse and is vulnerable to scour. An assessment should be undertaken to determine susceptibility, this should be carried out in accordance with the requirements set out in ‘BD97/12 The Assessment of Scour and other Hydraulic Actions at Highway Structures’.
6. Introduce performance measurement of structures, initially with reference to performance indicators relative to condition and capacity, progressing to the implementation of Availability and Reliability based performance indicators.
7. Undertake regular reviews of the Structures Asset Management Plan in order to ensure continued relevance and compliance with national guidance and codes of practice.
8. Continue implementation of the South Tyneside Council Structures Lifecycle Plan for Highway Bridges, Footbridges and Retaining Walls.

Highway Structures

Structures Lifecycle Plan for Highway Bridges, Footbridges and Retaining Walls

Addendum to SAMP - Section C, Code of Practice for Well Managed Highway Infrastructure