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 that span over or otherwise interact with the highway. Not glamorous, perhaps, but they’re 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.
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 (TAA), KCC will need to sign off any proposal, including private development, to construct, widen, assess, improve, repair or demolish a Highway Structure.
A range of technical documents providing more detailed guidance and specifications (PDF) is available via structurestechnicalapproval@kent.gov.uk.
You should consult the TAA 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)
- 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
More generally, developers and stakeholders need to consider the following:
All Highway Structures must be designed in accordance with the latest published standards and codes of practice; typically Eurocodes and the 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 We will not accept designs to superseded or inappropriate standards.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. If they’re not, you risk delaying the approvals process, 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 Agreement or Licence with the landowner.
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.
Further Guidance and Best Practice
Highways England – Design Manual for Roads and Bridges
Health & Safety Executive – Construction Design and Management (CDM) Regulations 2015
European Commission – Eurocodes