Romford to Upminster are served by Ilford EMU Depot, Chingford sidings and Gidea Park Sidings. A predecessor to modern maintenance free sidings was asphalt brick siding. There are sidings at High Barnet for stabling trains overnight. These locos were housed at Gloucester Carriage Sidings where Advenza Freight was based. The factory also had its own railway sidings and branch canal. There are several disused sidings on the beach at Dungeness. The diesel engine enables the locomotive to shunt on unelectrified sidings. As interurban routes tended to be single-track this led to extensive use of passing sidings. These included Portland Harbour and Holyhead Breakwater, which used a locomotive for working sidings. Stabling sidings and bay platforms at Portsmouth & Southsea station are co-ordinated from the depot. The line has four sidings used for storing rail cars. It covers and was the site of railway sidings until 1989. The Metropolitan line ends at Amersham, where there are turnback sidings just beyond the platforms. Signals are generally not provided for controlling movements within sidings or yard areas.