Man arrested, impersonated police officer

One man has been arrested while police search for another after the pair allegedly stopped three vehicles and impersonated police officers in Adelaide's western suburbs.

One suspect, who drove a red Holden Commodore sedan, stopped the first car on Thursday at about 2:15pm.

He spoke to the driver of the vehicle and identified himself as a police officer.

Early Friday morning, the two suspects stopped another car when they both identified as officers and issued a fine to the driver.

They drove him to a petrol station to withdraw money and after taking him back to his car, took the money and drove off.

The third incident happened just before 1pm on Friday when the suspect stopped another car and allegedly showed a badge to the driver.

The victim questioned the suspect and he returned to his car and drove off.

None of the victims were physically injured.

A 34-year-old man was arrested later that night and was charged with impersonating a police officer, unlawful detention, aggravated robbery and driving disqualified.

Police are still searching for the second man and urge anyone with information to contact Crime Stoppers on 1800 333 000.