A constable posted with the transport department was allegedly mowed down by a truck on Mathura Road, police said here on Monday.
The deceased, identified as Gagan Dahiya (40), worked at the Rajpur Road Authority office in the Civil Lines, they said.
The incident took place around 5.30 am on Sunday when he signalled a truck to stop for checking, they said.
He was taken to the AIIMS Trauma Centre where the doctors declared him dead. He sustained severe injuries on his head, police said.
A case was registered at the Sarita Vihar police station and the accused driver, Mohammad Tarif, was arrested, a senior police official said.
Tarif had come from Nuh in Haryana and has been carrying industrial chemicals from Rajasthan and Haryana, he said.
Gagan, who earlier worked for the Indian Army, is survived by his wife and two children, he added.