Highway Structures are the bridges, culverts and subways that take transport links over or under physical obstacles; they also include retaining walls and other supporting structures, and miscellaneous structures (such as reinforced earthworks) that span over or otherwise interact with the highway.
These highways elements are complex and safety-critical, with their own specialist inspection regimes and long-term maintenance requirements, so your design should ideally minimise or avoid them wherever possible.
It is important to engage with the Highways Structures team at an early stage about any planned changes to relevant infrastructure. If your scheme does involve a Highway Structure, this needs to be identified at the outset and discussed with KCC. As the Technical Approval Authority, KCC will need to sign off any proposal, including private development, to construct, widen, assess, improve, repair or demolish a Highway Structure. KCC has a range of technical documents providing more detailed guidance and specifications, which can be requested by emailing the Highways Structures team.
Generally, developers and stakeholders need to consider the following in relation to Highways Structures:
- All Highway Structures must be designed in accordance with the latest published national standards and codes of practice; typically Eurocodes and Design Manual for Roads and Bridges. We will not accept designs to superseded or inappropriate standards.
- Under the CDM Regulations 2015, your design consultant must be appropriately qualified and experienced, familiar with approval procedures and up-to-date with the latest design standards and requirements. By this, we mean chartered engineers with either the Institution of Civil Engineers (CEng MICE) or the Institution of Structural Engineers (CEng MIStructE) If they’re not, you risk delaying or potentially ceasing the approvals process altogether, incurring extra costs and having your structure judged inadequate, preventing adoption of the highway.
- Where KCC is to adopt a Highway Structure, this must be specifically written into the appropriate agreement, together with the payment for future maintenance. If not, you’ll need a Maintenance Deed or Licence with the landowner. An oversailing licence may also be required where a structure is overhanging the highway.
- Structures likely to be offered for adoption include bridges, subways and underpasses carrying public highway, retaining walls within the highway boundary, cantilever signs and signal gantries.
- Structures which will not be offered for adoption include retaining walls outside the highway boundary, parts of buildings or other structures attached to buildings projecting over the highway, and structures to be owned by other authorities, such as Network Rail or Highways England.
- Culverted watercourses, and other culverts, subways or underpasses carrying highway not maintainable at public expense may be adopted by KCC, or remain the landowner’s responsibility under a maintenance agreement.
- You’ll need Technical Approval for any proposals to install, remove or alter safety barriers or associated road restraint systems.
When proposing Highways Structures, KCC should be consulted on issues including:
- Retaining walls supporting the highway, such as basements – these need to be designed to withstand traffic loading
- The need for edge protection (parapets), and associated road restraint (safety barriers)
- Structures overhanging the highway boundary – this could be balconies, gantries, and even eaves
- Vertical clearance – the minimum headroom required for a particular route
- Horizontal clearance – kerbs and offsets to parapets
- Hydraulic capacity, as set by Environment Agency, Internal Drainage Board or KCC Land Drainage, and allowance for freeboard
- Access for inspection and maintenance, including easement areas
- Road construction and fill to buried structures
- Provision for future services, and interference with existing services
- Temporary works required to support the highway during construction – these may require separate approvals
- Geotechnical schemes such as soil nailing, chemical stabilisation, reinforced embankments and suchlike