1913. The section between Gates Avenue and Van Siclen Avenue was completed in 1885 as part of the BMT Lexington Avenue Line. From Alabama Avenue to just before the current Cypress Hills station, the Jamaica Line operates on the oldest elevated structure in New York City, a steel-reinforced cast iron line opened in 1893. East of Broadway Junction, a third middle trackway exists and elevates over the other two tracks, ending just west of the Alabama Avenue station. This track was intended to be an express track, but engineering studies completed after the work started indicated that the vibration of trains passing over the stations would be too severe and would literally shake the stations apart. Between Crescent Street station and Cypress Hills, the line runs on an "S-curve", turning north from Fulton Street onto Crescent Street, then east onto Jamaica Avenue. The curves are at nearly 90-degree angles, forcing trains to drastically reduce speed to 15 miles per hour in order to traverse them. The line east of Cypress Hills is known as the Jamaica Avenue Line, the newest section of the line which was built under the Dual Contracts. This structure has provisions on its entire length for three tracks, but a center track was never built (see below), with the exception of a layup track at 111th Street and another between 160th Street and 168th Street on the now-demolished original end of the line. Four curves on the line, including the two on the Jamaica Avenue "S-curve", are among the 30 sharpest curves in the subway system. The curve west of Marcy Avenue has radii of for Manhattan- and Queens-bound trains, respectively. The curve from Broadway Junction to Alabama Avenue has a radius of . The curve east of Crescent Street has radii of and the curve west of Cypress Hills has radii of , both respectively for Manhattan- and Queens-bound trains. As with other BMT Eastern Division lines, the Jamaica Line can only accommodate trains with eight or eight cars. Due to the narrow turning radiuses of the lines, cars (R44, R46, R68, R68A) could not be used on the Eastern Division. History The Union Elevated Railroad, leased to the Brooklyn Elevated Railroad, opened an elevated line above Broadway from Gates Avenue northwest to Driggs Avenue in Williamsburg on June 25, 1888. This was a branch of the existing Lexington Avenue Elevated, which then ended at