12.3 Maintaining Bridges and Structures

We will maintain our our highway structures with care and efficiency so that they are safe and ensure the highway network is readily accessible.

On the public road network in Lancashire, excluding the Trunk Roads, there are currently;

• 1449 bridges and 324km of retaining walls owned by the County Council
• 339 bridges and 69km of retaining walls owned privately.

These highway structures are an essential component of the highway network and it is paramount that they are well maintained and, if necessary, strengthened. In developing a strategy for this work, the highway structures must be considered in relation to the maintenance of the road they carry and also to the overall management of the relevant route. The County Council co-operates with private owners to ensure that the strategy also covers their structures.

The County Council is also responsible for the maintenance of footbridges on the Public Rights of Way Network. These structures are an important element of the Public Rights of Way Network and we will work to maintain and improve the condition of the network.

12.3.1 Code of Practice

The UK Bridges Board and DfT issued the third draft of the Code of Practice for Management of Highway Structures in March 2005 and the final document is due to be published later in 2005. This Code is to act as an authoritative reference and is intended to assist owners and managers in the implementation of recognised good management practice.

Lancashire County Council had a direct involvement in the production of the Code, as an officer of the Council was a member of the project team, and a substantial amount of the Code is based on the strategies, principles and practice already adopted by the County Council in the management of its structures. The County Council is therefore already working to many of the principles laid down in the Code and will aim to adopt the full Code following its publication. Implementation of this Code will assist the Council to deliver the LTP to the public in the most cost effective manner as detailed below.

12.3.2 Asset Management

The Code of Practice recommends the use of an Asset Management framework for the management of highway structures based on an Asset Management Plan in order to deliver an improved level of planning and good management practice. The County Council Structures Asset Management Plan is being developed as part of the Transport Asset Management Plan described in Section 7.1. Work to collect the required additional data for the Bridge Management System (BRAHMMS) began in 2004/05 and will continue, to enable the Asset Management Plan to be implemented.

12.3.3 Inspections

The data provided by inspection is fundamental to highway structure management and in order to fulfil the County Council's corporate objectives (see Section 7.1), inspection of the structures stock will continue to be undertaken in accordance with the Council's current practice to evaluate its condition. The additional requirement of the Code of Practice to undertake regular Principal Inspections will require further resources and its adoption will be implemented on a prioritised basis.

A new inspection system developed on behalf of the CSS Bridges Group was introduced in Lancashire in 2004/05, and by 2006/07 it will be possible to calculate the average Bridge Stock Condition Index (BSCI) for the whole structures stock. Until then, a conversion of the Lancashire Condition Indicator (LCI) will be used together with the BSCI to monitor the condition of the stock.

12.3.4 Bridge Stock Condition Index

The County Council is undertaking dual reporting of inspections and the results so far received have been used to produce a draft conversion of the LCI to the BSCI. Lancashire Condition Indicators from 1992 to 2004 have been converted to the BSCI system and are shown in Figure A.3.4  together with the future trajectory related to the level of funding.

It must be noted that the calculation of the trajectory is based upon a small sample of known data in order to illustrate the potential of the BSCI method. Consequently the trajectory will be refined annually as more data becomes available and the performance measurement framework is finalised.

A target BSCI of 93 has been set. This lies in the BSCI range 90 to 94 which defines the condition of the structure stock as 'Good'. The County Council considers that this represents a realistic target to ensure the structure stock is in good condition and presents a low risk to public safety. Once the target is reached, resources could then be concentrated on preventative maintenance activities. As a target BSCI has not yet been agreed nationally, the County Council intends to compare its target of 93 with those being developed by similar adjacent authorities.

Figure A.3.4 shows that the continuous decline in condition shown from 1992 onwards had halted in 2003/04 due to higher allocations between 1998/99 and 2002/03. However, the effect of a low allocation in 2003/04 is yet to become clear due to the time lag between expenditure and inspection.

In order to maintain the BSCI at the current value of 85, it is estimated that a funding level above that allocated for 2005/06 will be required for subsequent years. The implementation of a Value Management process (as described below) is expected to release funds from strengthening works that can be put to maintenance works. It is anticipated that a saving of £0.5 million per annum from this process would begin to address the maintenance backlog and consequently lead to an increase in the BSCI from its current value of 85.

12.3.5 Prioritisation of Schemes

In the previous LTP the strengthening of substandard bridges was the main priority and as a consequence Other Structural Maintenance was only carried out where it was considered that the work was essential to the stability of the structure or the safety of the travelling public. This short term policy, together with past underfunding, has resulted in deterioration of structures which as a consequence has led to a backlog of maintenance.

This LTP addresses the issue and highlights that, to provide the best possible value for money, maintenance work must be carried out at the optimum time. This would ensure that structures do not deteriorate to the extent where preventative maintenance is no longer possible, obviating the need for essential maintenance works and thus preventing an escalation in maintenance costs.

The County Council therefore intends to introduce a system which prioritises all works in order to achieve the best value for money through Asset Management. The Highways Agency has developed a method for Value Management of capital work for their annual bidding process that identifies need, prioritises this need, value manages possible solutions, scores the delivered benefits and identifies the optimum solution. The County Council gained expertise in the use of this method whilst acting as the Highways Agency's agent for Area 17 from 1999 to 2003 and intends to adapt this proven method to prioritise its highway structures work.

The County Council's Value Management process will examine likelihood and consequences of risk, taking into account safety, structure condition, structure capacity, accident records, traffic flows, availability of alternative routes and environmental impact. It will also incorporate socio-economic factors not included in the Highways Agency method, but which have been part of the County Council's own prioritisation process for strengthening works for some time.

12.3.6 Assessment

Assessment of structures is part of the Asset Management regime and provides information about the load carrying capacity of the structures and their ability to meet current and future performance requirements. The 40 tonnes assessment programme for bridges documented in the previous LTP is substantially complete.

The planned assessment of retaining walls has commenced and supplements the ongoing practice of ad hoc assessment of retaining walls that show signs of distress.

Once assessments of all structures have been completed, the County Council will introduce a prioritised programme to undertake 'steady state' assessments for structures in accordance with the Code of Practice, when conditions or events occur that increase imposed loads and/or reduce the load bearing capacity of the structure.

12.3.7 Management of Substandard Structures (Interim Measures)

Structures that have been assessed and do not meet the current highway loading standards are considered to present a risk to the public and appropriate interim measures are implemented until strengthening can be undertaken. These measures include narrowing of carriageway to avoid loading on weak portions of deck, measures to discourage vehicles over-running weak footways and verges and weight restrictions imposed on bridges. Consultation is undertaken with emergency services, public transport providers and members of district and parish councils prior to the implementation of these measures.

In some situations the social, environmental and economic consequences of imposing interim measures are considered unacceptable. These include severe disruption to traffic and bus services, adverse economic effect on businesses and safety implications of heavy goods vehicles using unsuitable diversions. In order to reduce the risk to the public, the frequency of inspections to monitor the condition of these bridges for deterioration has been increased.

12.3.8 Strengthening and Other Permanent Measures

In the previous LTP, priority was given to the strengthening of substandard bridges. However, as described above, the work necessary to bring the substandard bridges and retaining walls up to full capacity must be added to the structures workbank and value managed alongside all other maintenance work. As a result of the expected change in the priority of strengthening work, it may be necessary to consider making interim measures permanent as an alternative to strengthening where the social, environmental and economic consequences are considered acceptable in order to release funds which would have been used for strengthening and make them available for maintenance works. This change will improve the overall condition of the structure stock and help to achieve the County Council's target BSCI in a shorter timescale.

In partnership with Network Rail, a draft forward programme has been agreed for strengthening of Network Rail owned structures. This programme will be subject to the Value Management process described above and it may prove necessary to introduce permanent measures such as weight restrictions and footway protection as an alternative to strengthening.

Where strengthening is to take place, the schemes will be prepared with sensitivity to the environment and where possible the existing deck will be retained and strengthened with minimal effect on its appearance, for example, saddling of historic masonry arch bridges and reconstruction of the deck slab on existing steel girders to achieve better distribution of load and composite action. For each scheme, consultation will take place to engage the public and minimise disruption during the works.

Asset Protection

The County Council has several processes in place to protect structures and maintain the safe operation of the public highway in partnership with other owners and third parties. 

The management of abnormal loads is an operational process that forms part of the Asset Management Regime and is already in use. The process ensures that the load effects induced by the abnormal loads do not exceed the capacity of the structures on the route.

All structures on the highway network have been designated Streets of Engineering Difficulty as defined in the NRSWA 1991 and hence given protection from the works of statutory undertakers in the proximity of the structures.

In addition to the above processes included in the Code of Practice, the County Council is continuing to work in partnership with Network Rail to upgrade the signing of low railway bridges. Additional measures such as improved road markings, removal of overhanging vegetation, conspicuous painting of bridge fascias and use of overheight vehicle detection equipment are implemented where possible. These measures are designed to reduce the incidence of bridge strikes and the consequential disruption to both road and rail users, and to improve road safety on the highway and rail networks.

12.3.9 Performance Indicators

The County Council proposes to continue to report on the numbers of outstanding bridge strengthenings, retaining wall assessments and retaining wall strengthenings in partnership with members of the North West Area Bridge Conference.

In addition, as part of the implementation of its Asset Management Regime, the County Council intends to report on its structure management policy using the proposed national Performance Indicators developed by the Highways Agency and CSS Bridges Group. An officer of the County Council represented the CSS on the steering group for the production of this document.

These Performance Indicators are described in detail in the Draft Guidance Document for Performance Measurement of Highway Structures. The four indicators are Condition (using the BSCI mentioned above), Availability, Reliability and Measuring the Structures Workbank. The County Council will work to develop the indicators to enable feedback to be given on the draft guidance document by February 2006 with a view to implementation beginning in March 2007.

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