A motorcyclist crashed and died after braking as he approached a speed camera van.
Witnesses say the rider lost control before hitting the central reservation.
The 64-year-old was pronounced dead at the scene, on the A338 in Bournemouth on Saturday morning.
The rider, who has not been named, was from the Bournemouth area.
A Dorset Police spokesman said: "Due to the proximity of the stationary safety camera van at the incident, the matter has been referred to the Independent Police Complaints Commission."
The crash took place on the north-bound carriageway of the A338 at Cooper Dean Flyover.
Steve Craig, a local motorcycle instructor, said a speed camera van was often positioned on a bend at the site, just before the limit changes from 50 to 70mph.
“If it’s where I’m thinking it is, there is a bend there,” he said. He said the camera came into view “from about 100 metres” away.