Drivers are being stopped on parts of the M1, in the East Midlands, for a two week survey looking at the possible widening of the motorway.
The research, which started on Wednesday, forms part of assessment work being carried out into the possible widening of the carriageway between junctions 21 and 30.
The Highways Agency wants to get an overall picture of travel patterns in Derbyshire, Leicestershire and Nottinghamshire.
Drivers are being stopped at random and asked questions about their journeys.
Police are controlling traffic in survey locations and the Highways Agency says disruption will be kept to a minimum.