At 35 minutes, the film would have benefited from a more fleshed-out approach to its subject matter, which involves the 2015 arrest of Breaion King, a young African-American schoolteacher, in Austin, Texas. Yet the prolonged video of the encounter — in which police officer Bryan Richter pulled King from her car, slamming her to the ground despite her screams and pleas — illustrates the tensions between law enforcement and minority communities in a stark, sobering manner.Unlike most videos that play on the news of police stops gone wrong, nobody winds up dead here. But director Kate Davis allows the footage to play out much longer than the snippets to which cable news viewers are usually exposed, in addition to showing the arrest's aftermath.Beyond how quickly the incident escalates, that last part might be the most illuminating and provocative portion of "Traffic Stop." First, the officer provides a self-serving account of what happened that's just close enough to the what viewers witnessed to sound plausible — lacking other evidence — including his admission that the 108-pound woman was too petite to have appeared to pose much of a threat.King is then shown riding to the police station with a supervisor who openly expresses sentiments about African-Americans' violent behavior in terms that clearly smack of racism and bias. That exchange captures a dynamic repeatedly shown to have tragic consequences, while eroding trust and fostering suspicion."Traffic Stop" nevertheless feels somewhat underdeveloped and incomplete, beginning with the fact that King's lawsuit against Richter is still pending. In a sense, this feels like the opening act of a feature-length film that would provide greater context, and more closure.The availability of video — either shot by police-issued cameras or civilians — often hasn't been enough to convince juries of police misconduct. Anyone watching with an open mind, however, would have to empathize with how King — simply trying to get to work — suddenly found herself face down, handcuffed and shrieking in fear and pain.While "Traffic Stop" might end prematurely, its grainy images are nevertheless another vital tool for bringing this issue into sharper focus — one that should inform the much-needed conversation about how police interact with people of color, hopefully before the next minor stop that ends in tragedy."Traffic Stop" will air Feb. 19 at 8 p.m. on HBO.