Cumbria Police say they are aware of a video circulating showing an interaction between a police officer and a member of the public on Tuesday (27 Oct) on the A6 near Stoneybeck roundabout.
T/Chief Superintendent Rob O'Connor said: "Cumbria Constabulary was conducting a training exercise in the area at the time and officers had closed the road for the safety of all road users.
"The car was stopped at the road closure and part of the interaction between the Officer and driver was filmed by a member of the public.
"The Constabulary shares the concerns raised regarding the manner the driver was spoken to by the officer. As such, the incident is being investigated by the Constabulary’s Professional Standards Department.
"We have visited the man to apologise on behalf of the Constabulary and have also spoken to witnesses who are assisting with our investigation.