D.C. Transit Police want your help identifying a man who beat a Metrobus driver in Northwest D.C. early Friday after the driver asked the man to pay his fare.

A man boarded the bus at North Capitol and P streets NW and tried to ride without paying, police say. The driver asked for the man's fare and the man then punched the driver repeatedly, disturbing surveillance video footage shows.

As the attacker pummeled the driver, a good Samaritan intervened. He grabbed the attacker, wrestled him away and pushed him off the bus, the video shows.

The attack left the driver with a black eye, and his glasses were broken. It occurred about 7:50 a.m. on a 90 bus headed westbound on Florida Avenue NW, a Metro spokesman said.

The incident is the 69th attack on a bus driver this year, Metro Transit Police Chief Ron Pavlik said.

"It's very alarming and this is something unfortunately our bus operators have to deal with," he said.

Anyone convicted of assaulting a bus driver can be hit with an enhanced penalty, under D.C. law. At least 170 Metrobus drivers were assaulted on the job between early 2011 and early 2014, the News4 I-Team reported.

All new buses purchased by Metro will be equipped with plastic shields to protect drivers.

"The shields definitely protect our operators, this type of personal protective equipment, no different than a hard sole shoe, protective gloves," Pavlik said. "It's another type of equipment to protect our operators."

Anyone who is able to identify the attacker is asked to call Transit Police at 202-962-2121 and reference case no. 2015-58069. Tips also can be sent via text message to MyMTPD.