Road structures are a key asset group in a road network. They often critical points of risk (a broken structure makes a whole road inaccessible) and require support from a specialist structural engineer to manage over the long term.
Types of Structures that Cross Water
| Type | Definition | Photo Example |
|---|---|---|
| Bridge | A bridge is a structure that carries a roadway or over a physical obstruction, such as a river, lake, or even another road or railway. |  |
| Major Culvert | A major culvert is a tunnel structure that allows running water to pass under a roadway or railway. Culvert is also useful for water drainage or bridging the gap over a physical obstruction. A major culvert is where the cross section area is greater than 3.4m2 and therefore managed as a structure. |  |
| Causeway | A causeway (also known as a low-water crossing, low-water bridge or ford) is a low-elevation roadway traversing over a waterbody that stays dry above the water when the flow is low, but is designed to get submerged under high-flow conditions such as floods. Occassionally it is always wet with low flows. |  |
| River Crossing | A river crossing (also sometimes known as a ford or a wet crossing) is a shallow place with good footing where a river or stream may be crossed by a vehicle getting its wheels wet. A river crossing may occur naturally or be constructed. River crossings are likely to be impassable during high water. A River Crossing is not a structure but is often used to identify where a structure may be needed. |  |
Bridge vs. Culvert
A bridge is different to a culvert primarily because it is constructed of piers, abutments and a deck, where a culvert is all enclosed as either circular (tube) or rectangular with two sides, a floor and a roof.
Other Structures
| Type | Description | Photo Example |
|---|---|---|
| Tunnel | A tunnel is a passage built underground, for example to allow a road or railroad to go through a hill or under a river. A tunnel can be like an extra large culvert but for the purpose of carrying vehicles rather than water. While most tunnels are lined some tunnels can simply be a passageway dug through hard rock and requiring no lining. |  |
| Retaining Wall | A retaining wall is a relatively rigid wall used for supporting soil laterally so that it can be retained at different levels on the two sides. Retaining walls are structures designed to restrain soil to a slope that it would not naturally keep to. Retaining walls incluse seawalls as they are fundamentally the same type of structure. |  |
| Gantry | A gantry is a structure that crosses over an area and can be used to display, support or suspend objects (e.g. ITS equipment or cameras). |  |
Erosion Protection
Not strictly a structure but sometimes like a light retaining wall where its purpose is to stop erosion rather than retaining the earth behind it.
| Type | Description | Photo Example |
|---|---|---|
| Erosion Protection | Erosion protection is an asset or assets that have been placed or constructed to limit or prevent soil from being washed away by water or blown away by wind. |   |
