Lt. Christopher Micciche of the D.C. police said the driver was not cited because he had a green light when his vehicle struck the three on Friday night.
He said witnesses told police that the three pedestrians "either ran toward or jumped in front of the moving vehicle." He said one pedestrian jumped on the hood of the car. One of them was cited for being in the roadway.
"The protesters were apparently trying to block the roadway," Micciche said. "It was essentially an accident where three individuals were injured but they were in violation by being in the roadway."
D.C. fire department spokesman Lon Walls said Saturday morning that the three were transported to two area hospitals with non-life-threatening injuries.
Hundreds of protesters affiliated with Occupy DC shut down streets Friday near the city's convention center in downtown, where a conservative group was gathering.
The male driver of the vehicle was traveling southbound on 7th Street NW at K Street NW when the accident occurred at about 10 p.m.
The names of the driver and protesters were not immediately available.
One protester, 29-year-old Jesse Folks of Riverdale, Md., told The Washington Post that he was standing in the street with other demonstrators near the convention center when the car "just gassed it into a bunch of people."
"We were in the street, but this guy didn't even give us a chance to get out of the way," Folks said.
Micciche said witnesses provided a different account.
"They probably thought the driver would either stop or be able to stop, but it didn't appear that was the case."