Business drivers using satellite navigation should keep a map for backup, says the IAM (Institute of Advanced Motorists).

A recent survey revealed that 20% of women and 30% of men have blindly followed a satnav into the middle of a field, and Network Rail has experienced damage to railway bridges and level crossing collisions as a result of drivers’ failure to use their initiative.

Peter Rodger, IAM chief examiner, said: “Satnavs can be a real aid to road safety, providing the driver already has an idea of the route.

“Your satnav aids your own navigational abilities. It should not replace them. Have a map as a fall back and remember satnavs are no more infallible than the person who uses them, so do have some idea of your route before you set out.”