Nguyen Hoang Minh, 38, was detained by Hung Yen police Tuesday to be investigated for robbery.
Last Saturday, Minh was driving a 7-seat car on the Hanoi-Hai Phong Highway when he was stopped for speeding in Tan Tien Commune, Van Giang District.
Angry at being fined, Minh returned to the location after dropping off passengers in Hanoi. He parked the car about 50 meters away from the patrol team, climbed over the highway bar and repeatedly hit a police officer with a metal bar before stealing a radar speed gun and making his escape.
A search of Minh house in Hung Yen revealed a radar speed gun and other evidence in the case, police said.