After the Oklahoma City bombing in 1995 , the Secret Service closed the portion of Pennsylvania Avenue in front of the White House to all vehicular traffic . Pedestrian and bicycle traffic , however , was still permitted on the sidewalk . After 9/11 this policy was made permanent . Near the White House traffic is redirected to H Street or Constitution Avenue , both of which eventually link back with Pennsylvania Avenue . Plans drafted by District officials after the September 11th attacks call for Pennsylvania Avenue downtown to be used as a dividing line for any mass evacuation of the city . People north of the avenue would be directed north while those south of the avenue would be directed south . No vehicles would be allowed to cross the avenue
Oklahoma City bombing
Oklahoma City bombing
Pennsylvania Avenue