and Wodonga is double-track, but because of insufficient strength in the bridge only one train is allowed on it at a time. Other tunnel singling Hoosac Tunnel, Pan Am Railways, Massachusetts, US. Old Main Line Subdivision, B&O, Maryland, US. Entire subdivision was single-tracked to utilize higher clearances of the 9 tunnels on the line. Whitehall Tunnel, B&O, Pennsylvania, US. Wartime doubling Railways that become especially busy in wartime and are duplicated, especially in World War I, may revert to single track when peace arises and the extra capacity is no longer required. The Flanders campaign saw duplication of the Hazebrouck–Ypres line, amongst other works. Triple track Severe gradients made the headway in the uphill direction much worse than the headway in the downhill direction. Between Whittingham and Maitland, New South Wales, a third track was opened between Whittingham and Branxton in 2011 and Branxton to Maitland in 2012 to equalize the headway in both directions for heavy coal traffic. Triple track could be a compromise between double-track and quad-track; such a system was proposed south of Stockholm Central Station, but was cancelled in favor of Citybanan. In Melbourne and Brisbane several double track lines have a third track signalled in both directions, so that two tracks are available in the peak direction during rush hours. Triple track is used in some parts of the New York City Subway to add supplemental rush-hour services. The center track, which serves express trains, is signalled in both directions to allow two tracks to be used in the peak direction during rush hours; the outer tracks use bi-directional running and serve local trains exclusively in one direction. During service disruptions on one of the two outer tracks, trains could also bypass the affected sections on the center track. The Union Pacific Railroad mainline through Nebraska has a 108-mile stretch of triple track between North Platte NE and Gibbon Junction NE, due to a high traffic density of 150 trains per day. Portions of the Canadian National main line in the Greater Toronto Area and Southern Ontario are triple track to facilitate high traffic density of freight services, intercity, and suburban passenger trains sharing the same lines. India, through its state-owned Indian Railways has initiated the construction of a third track between Jhansi and Nagpur via Bhopal (approximately ) for reducing the traffic load and delays in passenger train arrivals. The construction between Bina &