Replacement of CR16 Horseblock Road Bridge Over Long Island Rail Road and Long Island Avenue

Engineering a Long-Term Long Island Bridge Replacement


Suffolk County, NY


Suffolk County Department of Public Works

Project Cost

$14.7 million


LiRo provided engineering services on a replacement for a major bridge carrying a highly-traveled route in Brookhaven, New York. LiRo first assessed the viability of the existing CR16 Horseblock Road Bridge that extends over the Long Island Railroad and Long Island Avenue, then recommended and designed a replacement for the existing deficient bridge.

About the Project

To evaluate the viability of the existing CR16 Horseblock Road Bridge—a four-span, steel-framed structure—LiRo began gathering information regarding current conditions. LiRo determined that the bridge’s deficiencies included inadequate width, deficient load capacity, substandard vertical alignment resulting in inadequate sight distance, seismic vulnerability, and non-redundant structural elements. Since the issues with the bridge could not be easily corrected through repairs, LiRo recommended replacing the bridge. LiRo then determined project needs and objectives, evaluated the consequences of proposed project actions, and prepared a design for the bridge replacement.

The final design calls for a new, more efficient two-span continuous bridge on the same alignment with additional width using steel plate girders. The bridge is located within an existing roadway network, which can accommodate a detour that will allow the bridge to be closed to traffic during construction so the demolition of the current structure and installation of the new structure can be completed during a single stage.

Project Challenges & Solutions

LiRo collaborated with the LIRR and NYSDOT as well as with the town of Brookhaven and utility owners to come up with the final design solution. NYSDOT’s involvement included approval of waivers for proposed vertical and horizontal clearances, which are less than the standards required and for conducting a public hearing to determine whether the project is in the public’s interest. LiRo developed and provided a tentative construction schedule to LIRR so it could prepare an estimate of costs associated with flagmen and bus service during the periods of construction when the track will not be operating so the existing bridge can be demolished and the new superstructure steel can be placed.


LiRo is providing construction administration services. The construction contract has been awarded, work commenced in spring 2019 and is expected to take a year to complete.


Civil & Structural Engineering