What action you take depends on what state you're in, and where the pedestrian is.
> Pedestrian crossing: 50 state summary
> The majority of states, however, only require motorists to yield to, rather than stop for, pedestrians crossing at uncontrolled crosswalks. Nineteen states require a motorist to yield when a pedestrian is upon any portion of the roadway. Louisiana mandates motorist yielding when a pedestrian is upon the same half of the roadway. Nebraska requires yielding when a pedestrian is upon the same half of the roadway or within one lane of the motorist. Massachusetts mandates yielding when a pedestrian is upon the same half of the roadway or within 10 feet of the motorist; and 20 states mandate motorists yield when a pedestrian is upon the same half of the roadway or approaching closely enough from the opposite side of the roadway to constitute a danger. In addition, in at least five states and the District of Columbia, bicyclists have the same or similar rights as pedestrians.
> Pedestrian crossing: 50 state summary
> The majority of states, however, only require motorists to yield to, rather than stop for, pedestrians crossing at uncontrolled crosswalks. Nineteen states require a motorist to yield when a pedestrian is upon any portion of the roadway. Louisiana mandates motorist yielding when a pedestrian is upon the same half of the roadway. Nebraska requires yielding when a pedestrian is upon the same half of the roadway or within one lane of the motorist. Massachusetts mandates yielding when a pedestrian is upon the same half of the roadway or within 10 feet of the motorist; and 20 states mandate motorists yield when a pedestrian is upon the same half of the roadway or approaching closely enough from the opposite side of the roadway to constitute a danger. In addition, in at least five states and the District of Columbia, bicyclists have the same or similar rights as pedestrians.
http://www.ncsl.org/research/transportation/pedestrian-cross...