How to measure a bridge crossing

Why Accurate Measurements Matter

Incorrect bridge measurements can lead to:
> Inaccurate quotations
> unsuitable bridge designs
> installation delays
> additional site costs

Measuring the Bridge Span

Measure the bridge length from the edge of one bank to the edge of the opposite bank, adding a minimum of 2 metres.
This allowance provides approximately 1 metre of bridge length beyond each bank edge.
As Bison bridges are stocked in 1-metre increments, selecting the next standard size up, for example an 8m bridge instead of a bespoke 7.8m unit, is often the most cost-effective option.

Other Important Measurements

Bridge Width

Consider:
> pedestrian and cycle use
> wheelchair access
> maintenance access
> future route usage

Bank Levels

Record any height difference between each side of the crossing, as this affects:
> gradients
> accessibility
> ramp requirements
> installation complexity

Watercourse Conditions

For river or stream crossings, assess:
> normal water levels
> flood risk
> erosion
> debris movement
A crossing that looks straightforward in summer can behave very differently during winter conditions.

Site Access Considerations

Before specifying a bridge, consider:
> vehicle access
> crane positioning
> restricted countryside access
> overhead obstructions
> ground conditions
Installation access is often one of the biggest overlooked challenges on rural bridge projects.

Site Photographs Help

Clear photographs can significantly improve quotation accuracy.
Useful images include:
both bridge approaches
> upstream and downstream views
> surrounding terrain
> access routes
> existing structures
Including a tape measure or person in photographs also helps provide scale.