trains make all local stops west of 71st Avenue during late nights to provide local service along the line. The routes experience frequent overcrowding during weekdays, and the Queens Boulevard Line has among the highest rush-hour train frequencies in the system. A planned upgrade to the line, to replace its signals with a communications-based train control system, would add capacity to the line. The line's construction in the 1920s and 1930s promoted housing growth along the Queens Boulevard corridor and stimulated the urbanization of central Queens. However, there are multiple provisions for spur routes along the Queens Boulevard line that were never built. The most notable of these proposals was the IND Second System, which would have provided a spur to Maspeth from the Jackson Heights–Roosevelt Avenue station; another spur to the Rockaways east of 63rd Drive–Rego Park via the Rockaway Beach Branch; a third spur east of Briarwood along the former Van Wyck Boulevard to South Ozone Park; and an extension of the line eastward past 179th Street. Other proposals included a "super express bypass" that would use the right-of-way of the Long Island Rail Road's Main Line to bypass all stations between 36th Street and 71st Avenue, as well as a spur from the Woodhaven Boulevard station northeast to Queens College via the Long Island Expressway. Route The IND Queens Boulevard Line begins with a large storage yard consisting of two levels with four tracks each south of 185th Street and Hillside Avenue. Once the tracks from the lower level merge with the tracks on the upper level, there is the first station Jamaica–179th Street (), and the line continues as a four-track subway under Hillside Avenue. Just after curving north under the Van Wyck Expressway, a flying junction joins the two-track Archer Avenue Line () to the local and express tracks. Soon after, the line turns west under Queens Boulevard. East of Kew Gardens–Union Turnpike, another flying junction ties the eastward tracks to Jamaica Yard. The other side of the wye curves west to become a lower level of the subway just west of Kew Gardens–Union Turnpike. After passing through 75th Avenue, those tracks join the local and express tracks at another flying junction. At Forest Hills–71st Avenue, the begin their westward routes. West of here, the line (now carrying the ) runs under Queens Boulevard until it turns north onto Broadway after Grand Avenue–Newtown. Near Jackson