Section 8.5 - Bridges and Boardwalks

The County Council as Highway Authority has a duty to maintain highways maintainable at public expense [Highways Act 1980 s41]. This also extends to the surface of bridges. Where dual liability exists the following policy sets out the County Council’s position.

Where there are public footpath or bridleway rights on a route, which also has private vehicular rights, the County Council may consider making a contribution towards the costs of maintenance of the surface to the extent required for the level of public rights. Where these private rights are carried over a bridge, the contribution will be made to the running surface only. The actual sum will reflect the cost to the County Council calculated as above, but may vary in accordance with the key principles. The contribution from the County Council would not normally exceed 10% of the cost of the appropriate maintenance works. [Policy 8-Executive Committee-Agenda item 4-29January2001]

This policy will ensure that the County Council does not waste money furnishing private rights where these are greater than the public rights over any given path.

For example, where a landowner wishes to resurface an access track suitable for cars and heavy agricultural vehicles and the route is also recorded as a footpath. The County Council would not normally contribute more than 10% due to the minimal requirements of the public rights. However, if the circumstance, for example, relates to a significant safety issue where the County Council could be negligent, the contribution may be more in order to ensure public safety.

Where this relates to a bridge carrying higher private rights the County Council would normally only be liable for maintaining the running surface – the equivalent of the top 2 spits. The County Council is therefore not willing to fund work beyond its normal liability.

New ditches, ponds and channels requiring bridging

It is an offence for a landowner to wilfully obstruct a public right of way [Highways Act 1980 s137]. The County Council has a duty to assert and protect the rights of the public to the use and enjoyment of the public rights of way network [Highways Act 1980 s130]. The following policy was endorsed in order to resolve obstructions caused by landowners constructing new ditches, ponds or channels across existing public rights of way.

Where a landowner creates a new ditch, pond or channel etc that crosses an existing right of way a suitable bridge or structure must be provided which can accommodate all legitimate users safely and without restriction. Structures may be supplied and erected by the County Council or approved agents. Landowners will normally be charged up to 100% of the reasonable costs of the installation. Where a structure is built to a higher specification, the County Council will bear the additional cost. Absence of any structure can be construed as 'wilful obstruction' on behalf of the landowner. Exceptions may include instances where a path is recorded in the Definitive Map and Statement subsequent to the new feature being created. [Policy 9-Executive Committee-Agenda item 4-29January2001]

This policy will ensure that landowners who intentionally obstruct rights of way, by creating ditches or water features, are required to provide a bridge or other suitable structure on the Definitive line of the right of way. Diverting the path retrospectively is not normally an acceptable solution and the feature will normally be considered an obstruction.

Higher specifications may include extra width beyond the minimum requirements, higher parapets and additional requirements where the route is considered appropriate for equal access. The County Council will still charge up to a minimum standard but will bear the cost of the higher specification. This approach is consistent with the County Councils aim to improve Access for All that is being promoted by the Disability Discrimination Act 1995 and obligations arising as a result of the Countryside and Rights of Way Act 2000.

Relevant legislation

Highways Act 1980

Section 91. Construction of bridge to carry existing highway maintainable at public expense

Section 92. Reconstruction of bridge maintainable at public expense

Section 328(2). Meaning of "highway"

8.5.1 New or replacement bridges

In the absence of any agreement:

• Where a bridge is constructed by another authority or landowner to cross an existing PRoW, responsibility normally lies with the person constructing; or
• Where PRoW comes into existence at a later date the responsibility for any existing bridge will remaining with the structure's owner. The Highway Authority is normally only responsible for the surface.
• Where shared rights exist liability will normally lie with the landowner where the private rights are greater than the public rights i.e. private vehicular rights across a bridle-bridge. The County Council may make a contribution to the maintenance cost in accordance with current policy in the Code of Practice for rights of way.
• Where a landowner creates a ditch, pond or channel that crosses a right of way they shall provide a suitable structure that can accommodate all legitimate users safely and without restriction.

Planning permission is not required so long as any works required for the maintenance or improvement take place within the boundary of the highway i.e. Where the bridge is not wider than the highway and it is required for the improvement of the PRoW.

Any culverting work affecting a watercourse (Mainriver or otherwise) will require written consent of the Environment Agency. They will also need to be informed of any bridge works on main rivers. Further details in Section 5.7.

8.5.2 Bridge Design

HCC will use the standard bridge designs where new or replacement structures are required. The designs, drawn up by independent consultants, are based on loadings and guidelines given by the former Countryside Commission for Scotland for structures carrying PRoW. These are the minimum standards that will apply to all PRoW.

The designs do not conform to the loadings for "Highway" footbridges under British Standard 5400, Part 2, as these are over engineered for most countryside applications. The specifications all meet current safety and loading requirements for rural paths. It may be appropriate to install wider structures depending on the category and status of the route. Where a larger structure is required a dedicated design should be drawn up with consideration for the DETR standards.

Technical Specification (Design loading)

• Main members: For normal conditions a loading of 2.3kN/m² is adequate. Where large crowds may gather, a figure of 3.2kN/m² must be used.
• Short span members: This is the necessary loading for the planks of a beam type footbridge, or the main members of a plank type footbridge. For pedestrian footbridges this should be the greater of 3.2kN/m² or 8.12kN (on a 175mm square) should be used.
• Parapets: This is the horizontal force applied at the top of the parapet posts. For pedestrian footbridges a figure of 0.74kN/m² at 1m high should be used. Should the structure be susceptible to crowd loading a force of 1.4kN/m² should be used. For bridlebridges a load of 1.3kN/m² should be allowed for at 1.25m above deck level.

Parapets

The purpose of a parapet is to prevent users of the bridge falling off and to make users feel safe when passing over a long drop or fast flowing river. Each situation is likely to be different, officers are at their discretion to provide parapets as necessary. The following criteria shall be used as a general guideline..

• Normally there would be none where the maximum drop is less than 1.5m.
• One parapet where the maximum drop from the deck is less than 1.5m and the officer believes it to be necessary, due to long span, high usage etc.
• Two parapets where the hazard spanned is a wide or fast flowing water-course and the maximum drop exceeds 1.5m.

Parapets should be at least 1m high for all normal situations and 1.4m high for hazardous situations. Required timber sizes will depend on the spacing chosen, posts should be 100mm x 75mm minimum, rails should be 50mm x 75mm minimum. Each situation will require a risk assessment and will depend on usage, particularly for horse users. Where there are gradients, sharp turns and other hazards, parapets should be considered.

8.5.3 Procedure

The landowner or occupier must be informed in all cases where a bridge requires installation or repair.

Access to the potential site(s) must be investigated. Unless access can be arranged for plant, workers and materials along the line of the PRoW, access times and routes must be agreed with the landowner.

The potential site(s) should be surveyed.

Decide if a bridge is necessary

There may perhaps be a simpler and less expensive alternative which should be considered where possible. These could involve alternative works such as creating a culvert, a land bridge or simple infill. Consideration should be given to the visual impact of any solution. Bridges often provide a positive experience for users of a PRoW.

Assess who will be using the bridge?

The range of users and expected volume is an important consideration. This will depend on the category and status of the route to be carried.

Consideration should be given to;

• the use of the bridge by farm traffic having private rights,
• the use of the bridge by children en route to school,
• the possibility of vandalism.

Consideration must be given to what will pass underneath the bridge. Statutory considerations may apply to a road or rail route, and responsibilities are often shared. If it is a main water course there is a need to consult with the Environment Agency and/or the local drainage board.

Other considerations

Consideration may be needed concerning the approaches to the bridge, is the existing line the best/only solution? The Highway Authority has the power to relocate a bridge up to 200yds either side of the route [HA80 s92], although this would necessitate a diversion order.

• Span (including foundations).
• Liability to flooding? Will it need anchoring to the ground?
• Are the banks stable? Are they level? What are the foundation conditions?
• Does the site have any conservation status (SSSI, NNR)? Are there trees near the site that may have Tree Preservation Orders on them? Will roots be damaged? Are there any branches overhanging?
• Are there underground or overground services in the vicinity?

Select bridge design

The designs and drawings produced by the consultants are for specific spans, and have been independently checked. Table 8 (below) provides guidelines for the applicability of the designs. Advice should be sought from a qualified bridge engineer for bridge construction projects with a span between 4m and 5.2m and a drop between 2m and 3m. Bridge construction projects with a span greater than 5.2m and or a drop greater than 3m should be designed and managed by a qualified bridge engineer.

Short span bridges should be erected to the appropriate standard. Guidance with respect to handrails, kickboards and decking can be found below in the section on boardwalks.

Table 8

Non-slip surfaces.

The decking of bridges are renowned for becoming very slippery in wet or damp conditions. Some solutions are outlined below:

1. Use of grooved decking.
2. Battens can be made from thin board to provide extra purchase on the decking surface.
3. Use of hobnails or galvanised and welded wire mesh, not chicken wire (25x25mm mesh is recommended.)
4. The surface can be covered with non-slip paint.
5. Use of cold tar with chippings or similar resin/aggregate compound.

No particular option is recommended, solutions should be decided on a case by case basis. The following considerations should apply.

Access for all: Options b and c may make it more difficult for some users especially those with wheelchairs, pushchairs and other mobility problems.

Environmental impact: Options d and e could be harmful to the environment where insufficient care is taken during the application. Such treatments can be applied off site where spillage can be better controlled or with care on site after installation. Surrounding soil and vegetation should be protected by covering in plastic sheeting during application.

Cost: The additional cost of non-slip treatment for a standard bridge is likely to be in the region of £40-50. Experience from other authorities suggest that similar treatments are hard wearing and therefore do not increase the maintenance commitment. Non-slip surfaces should therefore be considered wherever threats to public safety arise directly relating to the surface of the bridge.

8.5.4 Boardwalk specification

Boardwalks serve two useful purposes:

1. to provide a path across otherwise impassable terrain such as deep marsh or alongside streams.
2. to protect a fragile habitat, such as a bog, marsh or woodland floor.

Their use is not normally recommended on PRoW where hardening of the surface is normally the better solution.

Dimensions and materials

The required width depends on whether the boardwalk is designed to be one- or two-way, obligatory or voluntary, and on the numbers of people likely to be using it at any one time. Suggested widths are between 0.75m and 0.9m for one-way use, and between 0.9m and 1.2m for two-way use. Heavily used boardwalks must be at least 1.2m wide. The widths for wheel chair use are 1.2m and 2m for one-way and two-way traffic respectively.

Boardwalks are best constructed of timber and comprise four distinct elements:

1. Foundations

For most normal purposes foundations will be unnecessary. In special cases the recommended dimensions are a 0.6m x 0.6m hole to be lined with a geotextile and filled with stone or concrete. The boardwalk bearers can then be stood on this foundation.

2. Bearers or stobs

Use of stobs is recommended as they require less timber than bearers and levelling is easier. However, bearers will be required on soft ground to prevent the boardwalk from sinking.

Stobs and cross-beams should be constructed from minimum 0.1m square section timber. They should be no more than 2m apart, however sections over 2m will require three stobs.

Bearers can be formed from railway sleepers, sawn timber or local logs. Railway sleepers sawn in half are sufficient to support a two-way boardwalk.

3. Decking

Decking shall be laid transversely, with a maximum gap of 20mm. Boardwalks intended for use by people with disabilities (and their carers) or parents with children should have a maximum gap of 12mm. Decking can be attached to the stringers, flush or with an overlap. The former provides a neater finish that is more resistant to vandalism, the latter is structurally stronger as the unsupported dimension is reduced. Overlaps of between 50-100mm are suitable for narrow to wide boardwalks respectively.

Non-slip surfaces.

The decking of boardwalks are renowned for becoming very slippery in wet or damp conditions. Some solutions are outlined below:

1. Use of grooved decking.
2. Battens can be made from thin board to provide extra purchase on the decking surface.
3. Use of hobnails or galvanised and welded wire mesh, not chicken wire (25x25mm mesh is recommended.)
4. The surface can be covered with non-slip paint.
5. Use of cold tar with chippings or similar resin/aggregate compound.

No particular option is recommended, solutions should be decided on a case by case basis. The following considerations should apply.

• Access for all: Options b and c may make it more difficult for some users especially those with wheelchairs, pushchairs and other mobility problems.
• Environmental impact: Options d and e could be harmful to the environment where insufficient care is taken during the application. Such treatments can be applied off site where spillage can be better controlled or with care on site after installation. The surrounding soil and vegetation should be protected by covering in plastic sheeting during application.
• Cost: The additional cost of non-slip treatment for a standard bridge is likely to be in the region of £40-50. Experience from other authorities suggest that similar treatments are hard wearing and therefore do not increase the maintenance commitment. Non-slip surfaces should therefore be considered wherever threats to public safety arise directly relating to the surface of the bridge.

4. Handrails and kickboards

Where there are gradients, sharp turns and other hazards edge boards and/or handrails should be considered. Where the facility will be used by disabled persons some provision of edge protection should be given.

Handrails must always be strong enough to bear the weight of people leaning against them. The number of handrails will depend on the situation and the expected use. A single handrail on one side only gives minimum protection. In hazardous situations two or three rails on both sides should be used, with wire mesh if there is a risk to the safety of children or animals.

Handrails should be 1m high for all normal situations and 1.4m high for hazardous situations. Required timber sizes will depend on the spacing chosen, posts should be 100mm x 75mm minimum, rails should be 50mm x 75mm minimum.

Kickboards shall be fitted where it is deemed appropriate. They are often less intrusive than a handrail and are significantly quicker and cheaper to construct. The minimum dimension for a deck level kickboard is 75mm high. If a rail is used for edge protection its bottom edge should be no more than 75mm from the deck level.

Choice of line and profile

1. This must be within the definitive line of the PRoW.
2. Boardwalks in woodland, and marsh situations are typically hidden by vegetation and so the least cost (straightest and shortest) route is to be taken.
3. Boardwalks across open ground need careful siting and design. The appearance of a long boardwalk can be improved by the introduction of gentle angles or curves.
4. Construction of boardwalks on sloping ground require the introduction of stepped or ramped sections. Avoid straight lines wherever possible, curved steps appear easier to climb. Break up long flights with bends and ramps.
5. Each step should be no more than 0.16m high. Treads should be built with a rise from front to back to facilitate drainage and so as not to disrupt the natural rhythm of walking. Risers should be boarded up to neaten the appearance and to protect the stringer ends.

Where wheelchair access is required all paths must be level or ramped. (NB. Some disabled people can more comfortably and safely use steps.) Gradients greater than 5%, will require flat landings, at least 1.2m wide by 1.5m long, for every 0.75m of vertical climb. Slopes should not be greater than 10%. Guidance notes in BT Countryside for All - Sheet 2.1.