To address overcrowding, in 1909, the New York Public Service Commission proposed lengthening platforms at stations along the original IRT subway. As part of a modification to the IRT's construction contracts, made on January 18, 1910, the company was to lengthen station platforms to accommodate ten-car express and six-car local trains. In addition to $1.5 million (equivalent to $ million in ) spent on platform lengthening, $500,000 () was spent on building additional entrances and exits. It was anticipated that these improvements would increase capacity by 25 percent. At the 14th Street station, the northbound island platform was extended north and south, while the southbound island platform was extended north, necessitating the replacement of some structural steel north of the intersection of Fourth Avenue and 13th Street. Six-car local trains began operating in October 1910. On January 23, 1911, ten-car express trains began running on the Lenox Avenue Line, and the following day, ten-car express trains were inaugurated on the West Side Line. In 1918, the Lexington Avenue Line opened north of Grand Central–42nd Street, thereby dividing the original line into an "H"-shaped system. All trains were sent via the Lexington Avenue Line. Dual Contracts After the original IRT opened, the city began planning new lines. The New York Public Service Commission adopted plans for what was known as the Broadway–Lexington Avenue route (later the Broadway Line) on December 31, 1907. A proposed Tri-borough system was adopted in early 1908, incorporating the Broadway Line. Operation of the line was assigned to the Brooklyn Rapid Transit Company (BRT, subsequently the Brooklyn–Manhattan Transit Corporation or BMT) in the Dual Contracts, adopted on March 4, 1913. Because the Dual Contracts specified that the street surfaces needed to remain intact during the system's construction, a temporary web of timber supports was erected to support the streets overhead while the BMT platforms were being constructed. The Broadway Line platforms opened on September 4, 1917, as the northern terminus of the first section of the line between 14th Street and Canal Street. Initially, it only served local trains. On January 5, 1918, the Broadway Line was extended north to Times Square–42nd Street and south to Rector Street, and express service started on the line. The Dual Contracts also called for the construction of a subway under 14th Street, to run to Canarsie in Brooklyn; this became the BMT's Canarsie Line. Booth and Flinn was awarded the