In Philadelphia, a municipal block captain program gives involved citizens a chance to tackle problems on their streets. Studies have shown that block captains have mixed results at reducing crime levels, said Caterina Roman, a Temple criminologist. "You really need a motivated community leader that's going to sustain that effort," said Roman. "You can't go out and say, we're going to do this effort, do one walk a week for a few weeks and expect you are going to have an impact on crime."