Drivers on the A149 between King's Lynn and Hunstanton will be monitored by average speed cameras.

Plans to install the so-called yellow peril on the busy Norfolk coast road were announced last year, when the devices went live on the A17 between Lynn and Sutton Bridge.

Now a report reveals that multiple cameras will be placed at Knight's Hill, Castle Rising, Babingley and on the Dersingham bypass.

The route which will be monitored by the cameras includes the stretch which winds through part of the Royal Estate at Sandringham.

While the Queen normally travels at a sedate pace in her Bentley, officials say that there are higher than average numbers of collisions caused by excessive speed along the route.

Highways engineer Andrew Wadsworth said: 'The A149 north of King's Lynn, was identified as having a high rate of personal injury collisions during routine analysis of collisions on Norfolk's network.

'In particular, the predominant collision types are those which may be associated with excessive speed, such as tail end collisions overtake and head on collisions.

'It is recognised that average speed enforcement is an effective way of treating the types of driver behaviours which lead to these types of collisions and this has led to the design and upcoming installation of an average speed camera system, to be funded by Norfolk's Safety Camera Partnership.

'I do not have an exact installation date as yet, but it is hoped that the 6 sites can be installed before the summer embargo comes into force on the A149 on May 22.'

More than 800 drivers have been caught since an average speed camera system went live on the A17 between Lynn and the Lincolnshire border.

The devices can detect any kind of vehicle speeding including motorcycles. They scan both lanes in all weathers, day and night. ANPR cameras log the number plate of vehicles passing through the system, with time taken between two fixed camera points used to calculate average speed.

They are now believed to operate on more than 250 miles of Britain's roads. Changing lanes to defeat them is an urban myth.