A report published in the British Medical Journal suggests that speed cameras could reduce road deaths by up to 71%.

However, researchers who reviewed the findings of 14 separate studies found wide variations in the available data.

The review drew together research from different countries, including Britain, Australia, Canada and New Zealand.

It is described as the world's first systematic review on the effectiveness of speed cameras.

The review, which examined research on both fixed and mobile speed cameras, concluded that further, more detailed, work on the issue was needed.