The New York City Department of Transportation (NYCDOT) Seismic Design Guidelines Report was updated in September 2008 by Weidlinger Associates to reflect current state-of-the-art knowledge. The NYCDOT seismic design guidelines are for use in the Downstate Zone which consists of New York City, Rockland County, Westchester County and Nassau County. NYSDOT has adopted the AASHTO LRFD Seismic Design Specifications for the Upstate Zone. The NYCDOT Seismic Design Guidelines Report (September 2008) proposed for use in the Downstate Zone has some key differences with the current AASHTO LRFD Bridge Design Specifications.