Old Oak Common (OOC) is a railway station under construction on the site of the Old Oak Common traction maintenance depot to the west of London in Old Oak Common, approximately 500 m (1,600 ft) south of Willesden Junction station. When built, it is expected to be one of the largest rail hubs in London, at about 800 m (2,600 ft) in length and 20 m (66 ft) below surface level.