Replacement of the Roslyn Viaduct (Route 25A) over Hempstead Harbor, Village of Roslyn, Nassau County, NY

As part of a team, SIMCO performed an assessment of available traffic data and preparing Maintenance and Protection of Traffic (MPT) Plans, Details, Specifications and Estimates.

The Roslyn Viaduct was constructed in 1949 and functions as one of the main east-west routes on the northern shore of Long Island. The Viaduct is approximately one-half mile long with 2,775 feet of approach roadway and ramps. It is estimated that about 45,000 vehicles cross the viaduct on a daily basis. The viaduct is to be replaced with a new structure to meet current design standards and carry four lanes of vehicles as well as pedestrians and cyclists. Replacement of the viaduct must occur while traffic flow is maintained on the existing structure and four access ramps within the project limits without detouring any traffic onto the surrounding local streets.

SIMCO’s work effort had been initiated with project site field reconnaissance, a review of available data sources and preparation of an inventory of available data. As the project progressed, SIMCO investigated the feasibility of utilizing moveable barriers on the mainline to provide two lanes in the peak direction with one lane in the opposite direction for three stages of construction. A fourth stage was used for the median closure on the structure as well as the approaches. SIMCO prepared the Final Plans, Specifications and Estimates (PS&E) for this MPT.

In addition to the MPT work, SIMCO was responsible for the design of the traffic signal at the intersection of Bryant Avenue and Witte Lane which designed in accordance with Nassau County Department of Public Works (NCDPW) standards. To complete the design of this Nassau County traffic signal on the NYSDOT project the design was coordinated with the NCDPW Traffic Signal Unit.