Pedestrian safety advocates say walking in the city's car-congested streets can be deadly and the city should do something about it. Their plea for changes comes after a lethal weekend for pedestrians.Three people were killed after being struck by cars. In one instance, the driver sped away after hitting the pedestrian. The nonprofit group Transportation Alternatives wants the city to increase crossing times at some intersections and raise crosswalks.The group claims that 170 pedestrians were killed on city streets last year. The city's Transportation Department says that 163 died.