Mayor Bill de Blasio announced Thursday the expansion of the NYPD's community policing program into New York City's subways.

The police department has touted its 3-year-old program as a way to bridge the gap between officers and the community they serve.

The concept is simple: Officials say that the more familiar residents get with the officers patrolling their neighborhood, the better relationship they'll have.

With the subway program, officers and commuters will ostensibly have a chance to get to know one another.

The expansion underground will first launch on the No. 2, No. 5 and No. 6 lines in the Bronx and on a dozen lines in northwestern Brooklyn.