Business drivers using satellite navigation should keep a map for backup, says the IAM (Institute of Advanced Motorists).
Many people in rural areas will have seen or heard of lorry drivers getting stuck in narrow lanes after blindly following their satnav's cheerful instructions. 

If the UK were to introduce 'road trains' (articulated 60 tonne mega-liners stretching up to 82ft), as has been discussed recently, these incidents could be much more serious says the IAM.

A recent survey said 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. Drivers using satnavs for the first time should be prepared to familiarise themselves with it before setting off on a journey."

The IAM recommends:

*   Always programme your satnav before you set off, not while you are driving.
*   Use the audible instruction to guide you and only use the screen for a quick glance as a confirmation.
*   Certain routes may be closed for whatever reason, and sometimes the data on the satnav itself is old - with a map you can find routes around problems more easily. Pull over and look at your map at the first safe opportunity if you get confused.
*   Drivers should also think about the position of the unit - the satnav unit shouldn't obstruct your vision or be put where an airbag could be deployed.
*   Weight and height restrictions apply to some routes which is worth bearing in mind if you are driving a hired vehicle that is larger than one you are used to.
*   Remove the unit before leaving the vehicle and make sure that all visible satnav mounting marks are removed from the windscreen before you leave the car - they encourage thieves. Also don't programme in your 'home' details - thieves have been known to use these to commit further offences after stealing the satnav unit.
*   Although there is currently no legislation for the correct use of satellite navigation equipment, the police have a number of offences they can apply if they believe the driver to have been 'driving without due care' or 'failing to have proper control'. These could result in endorsements of between three and nine penalty points on your licence.