Structures Maintenance Plan
4. Hierarchy
4.1 In order to develop an inspection and maintenance regime commensurate with the locality, use, importance and consequence of failure, the following hierarchy has been developed using an informal risk assessment of the aforementioned criteria;
Hierarchy | Description |
|---|---|
Category 1 | Any load bearing structure that has been identified as a critical structural asset. |
Category 2 | Any bridge that · Carries or crosses a principal or classified road with a defined carriageway hierarchy of Cat 2, 3a or 3b**. · Carries or crosses an unclassified road that is either part of the Major Road Network, Strategic Route Network or is on a preferred abnormal load route. · Carries an unclassified road or footway that crosses or impacts upon Network Rail Property. · Carries an unclassified road or footway that crosses or impacts upon a main river. |
Category 3 | Any bridge that carries or crosses any carriageway or footway that does not qualify as a Category 2. Or Any other type of structure within the boundaries of any category of adopted highway. |
Category 4 | Bridges that are outside of the limits of the adopted highway (For instance are located on a Public Right of Way, leisure paths (maintainable at the authority's expense) or long distance footpaths). |
Category 5 | Structures, other than bridges, that are within the wider public realm. |
Category 6 | Other none load bearing culverts, pits, pipes, bridges or structures. |
** Carriageway hierarchies are defined in the Well Managed Highway Infrastructure Code of Practice (Oct 2016) Section A.4.3.11 Table 1
4.2 Critical structural assets are identified through a risk management process based on location, use and local knowledge and are generally defined as those assets within the Borough that fall within one or more of the following categories;
- may be at risk from regular flooding events
- serve large population, commercial or industrial areas with limited or no local diversion routes
- are on the Strategic Diversion Routes for the Trunk Road Network
- are large complex structures, the replacement of which would be extremely difficult
- structures which if lost or closed would isolate smaller rural communities
- carry any part of the resilient network
- are subjected to a significant number of abnormal load movements due to their proximity to heavy industry areas.
4.3 Historic or 'listed' structures are normally defined using the hierarchy categories detailed above but consideration is also given to the constraints placed upon them, when planning inspections or works, that may have substantial implications in terms of lead in times and financial costs.
4.4 The hierarchy of a structure is used to define the inspection regime to which the structure is subjected and can also be used in the prioritisation of maintenance works.
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