The incident took place near Dabur Crossing when the woman along with her brother was going to Mohan Nagar area from Delhi on a scooty.
Traffic Police Sub-Inspector Virendra Singh was managing traffic at the crossing.
"The scooty was hit by a car near Dabur Crossing. The woman then approached Singh for his intervention in the matter," said a police official.
The official said locals told the police that instead of helping her, Virendra got annoyed and misbehaved with the woman. This angered passersby who started beating him, he said.
"After the incident, Virendra was taken to hospital where he is recuperating. He has sustained injuries on the face and hands," the official added.
He said police were investigating the case and strict action will be taken against Virendra if he is found guilty.