Powell reportedly refused a breathalizer test at the scene and was taken into custody.
He was charged with driving while intoxicated.
Police say during the traffic stop, a 31-year-old woman was found passed out in the back seat of his car.
The woman was taken to St. Luke's Hospital for apparent treatment of intoxication, hospital officials say.
Powell was arraigned and released on his own recognizance pending his next court appearance.
His attorney say he is "certain that [Powell] is absolutely innocent, and will establish that clearly" in further court proceedings.
Powell represents East Harlem in the state Assembly.
Powell, 45, is the son of the late U.S. representative and civil rights activist Adam Clayton Powell Jr. After serving on the New York City Council from 1992 to 1997, Adam Clayton Powell IV was first elected to the Assembly in 2000.
In 2004, Powell was investigated by police in Albany over an allegation he sexually assaulted a 19-year-old legislative intern after a night of drinking in a motel room. The woman initially told police Powell provided her alcohol then forced her to have sex. Powell's lawyer later said the woman recanted.
Later that same year, the Manhattan district attorney's office cleared Powell in the report of an alleged rape of a woman in his Manhattan apartment.
He had been planning to run for public advocate.
On the web: http://assembly.state.ny.us/mem/?ad=068
