While the bridge has always permitted the passage of pedestrians, the promenade facilitates movement when other means of crossing the East River have become unavailable. During transit strikes by the Transport Workers Union in 1980 and 2005, people commuting to work used the bridge; they were joined by Mayors Ed Koch and Michael Bloomberg, who crossed as a gesture to the affected public. Pedestrians also walked across the bridge as an alternative to suspended subway services following the 1965, 1977, and 2003 blackouts, and after the September 11 attacks on the World Trade Center.