The viaduct provides a pedestrian-, bicycle-, and bus-free express route for taxicabs and other automobile traffic that flies above congestion from 40th Street to 46th Street. From the south, the roadway begins at 40th Street. From 40th to 42nd street, the central roadway of Park Avenue rises to a T above 42nd Street, shading the busy 42nd Street entrance to Grand Central Terminal below. Meanwhile, side lanes of Park Avenue descend from 40th to end at 42nd Street. The elevated roadway then encircles the Grand Central Station. Traffic from the south is diverted to the right, around the east side of the station, and descends again to Park Avenue at 46th Street north of the Pan Am Building Traffic coming from the north around the west side of the station is diverted south to 40th Street; barriers prevent traffic from recircling the station. The south end is fed by the Park Avenue Tunnel (roadway).
The viaduct appears in numerous movies and television show episodes. For one example, Will Smith's character in the 2007 film I Am Legend is captured by a vampire's snare there.