Road Bridge — Bridges & Culverts

Road Bridge is a structure that carries vehicular traffic over an obstacle — a watercourse, valley, railway or another road. UK road bridges are designed to the Design Manual for Roads and Bridges (DMRB) and the structural Eurocodes, with assessment loading governed by CS 454.

Main types of road bridge

Road bridges are classified by their structural form. Span length, ground conditions, programme and cost determine the most suitable type:

Type	Typical span	UK use case
Soil-steel composite (buried arch)	2–25 m	Highway and minor road crossings
Pre-cast concrete beam	10–40 m	Standard motorway and trunk-road bridges
Composite steel-concrete beam	20–60 m	Medium-span bridges over rail and rivers
Steel truss / box girder	30–200 m	Major motorway and estuary crossings
Cable-stayed / suspension	100–2,000+ m	Strategic crossings

Soil-steel composite bridges

Soil-steel composite (or buried) bridges are a fast-build alternative to traditional concrete or steel beam bridges for spans up to around 25 m. A corrugated steel arch or pipe-arch is buried in compacted granular fill; the soil and steel act together as a composite structure where the surrounding fill carries a large share of the load.

The technique is widely used in the UK for highway crossings of watercourses, railway underpasses and farm accommodation bridges. Installation typically takes 2–6 weeks against 3–6 months for an equivalent concrete bridge — making it attractive where road or rail closure time is critical.

Design standards in the UK

All new highway structures in the UK are designed to the DMRB, which adopts the structural Eurocodes (BS EN 1990 to BS EN 1999) with UK National Annexes. Loading uses Load Model 1 from BS EN 1991-2 for normal traffic and abnormal indivisible load assessment under CS 454.

Existing structures are assessed under CS 454 (formerly BD 21/01). The standard requires regular Principal and General inspections every 6 and 2 years respectively, and structural assessments at least every 6 years for the strategic road network.

Related ViaCon solutions

ViaCon delivers soil-steel composite road bridges and culverts across the UK — including the Helcor corrugated steel pipe system. See our complete bridges and culverts solutions and the broader product range at culverts. Related glossary entries: box culvert, pipe arch and temporary bridge.

Frequently asked questions about road bridge

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