Police are investigating complaints concerning the drivers of a number of performance cars, on the Mountain Road on Saturday.
They relate to overtaking manoeuvres, carried out between Ramsey and Douglas in the six and a half hours from 10am to 4.30pm.
Police say other motorists who were travelling on the road at the time may have information.
The numbers to ring if you can help the investigation are 631212, for Police Headquarters in Douglas, and the anonymous Crimestoppers line on 0800 555 111.
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