same time, the BRT moved to eliminate remaining operations that required elevated trains to operate under overhead wire. In most cases this meant using third rail on fully grade-separated lines. When third rail was extended on the Canarsie Line it was decided to extend this power mode only as far as the important station at Rockaway Parkway and Glenwood Road. Beyond that point, frequent grade crossings made third rail impractical. This portion of the line was converted to the Canarsie Shuttle using elevated cars in October 1917 and converted to trolley cars on October 18, 1920. One grade crossing was retained at East 105th Street despite the third rail, and was the last public rapid transit grade crossing in New York City. It was closed by 1973 as part of the Flatlands Industrial Park project, which was built on either side of the ground-level Canarsie Line. A pedestrian overpass above the tracks was built to replace the grade crossing. 14th Street–Eastern Line Initial subway The Dual Contracts also called for a subway line initially known as the 14th Street–Eastern District Line, usually shortened to 14th Street–Eastern Line. The line would run beneath 14th Street in Manhattan, from Sixth Avenue under the East River and through Williamsburg to Montrose and Bushwick Avenues in Brooklyn. Booth and Flinn was awarded the contract to construct the line on January 13, 1916. Clifford Milburn Holland served as the engineer-in-charge during the construction. A groundbreaking ceremony was held on April 8, 1916. The line's opening was delayed by several years. In 1922, John Francis Hylan blocked some construction contracts, claiming that the costs were excessively high. The Station Finish Corporation was contracted to build the stations in Brooklyn and the Charles H. Brown & Son Corporation was contracted to build the stations in Manhattan. Track-laying in the tunnels between Sixth and Montrose Avenues started by November 1922. Due to the city's failure to approve the section of the line between Montrose Avenue and East New York, the 14th Street/Eastern Line was initially isolated from the rest of the system. In 1924, a temporary connection was built from the Long Island Rail Road (LIRR)'s Bushwick Yard that ran via Montrose Avenue and then connected to the 14th Street/Eastern Line under Bushwick Avenue just near the Montrose Avenue station. This was done to allow the delivery of BMT Standard subway cars. The first of the cars were