Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Top-left photo Signs typically in place along the escalator and adjacent stairs, bottom-left photo the 45 signs (posters and banners with motivational messages) placed on alternate stair risers, pillars, and the wall, right schematic representation of the intervention site and the position of the observers
