A new attempt is being made to educate England's motorway drivers to keep in the proper lane.
The aim is to make better use of motorway capacity
Messages are being shown on signs on several motorways saying "Keep left unless overtaking" and "Don't hog the middle lane".
Highways Agency officials will be monitoring drivers' reactions as part of a campaign to reduce accidents.
The messages will be shown on parts of the M1, M6, M18 and M62 in the north of England and the East Midlands.
Roads Minister David Jamieson said: "Poor lane discipline causes frustration to drivers and can disrupt the flow of traffic.
"We have all seen people on the motorway sitting in the wrong lane and experienced the inconvenience and congestion it causes."
Messages are being carried at various points on motorways in South Yorkshire, Cheshire, Lancashire, Derbyshire, Nottinghamshire, Northamptonshire and Leicestershire.
The results of the week-long trial will be studied by the Highways Agency before deciding whether they should be a permanent feature of the motorway network.
In August the RAC Foundation said that drivers hogging the middle and outside lanes were "stealing" up to 700 miles of motorway space from other drivers in peak periods.
That is roughly equivalent to the distance from Aberdeen to Penzance.