of extensions to the Supertram network have been proposed. In May 2003, the South Yorkshire Passenger Transport Authority announced plans to extend the Supertram network to Hellaby, a suburb of Rotherham; Dore, a suburb of Sheffield; and Ranmoor, Sheffield. None of these extensions has been built. In August 2008, plans were announced for the trial of diesel-electro hybrid tram trains on a route via Network Rail tracks to Huddersfield via Meadowhall, Barnsley and Penistone. The fleet of five tram trains, costing £9 million was expected to be in operation by the end of 2010 with the whole project costing £24 million for the 37-mile route. It was planned that the hourly Northern Rail service from Sheffield to Huddersfield via the Penistone line would be scrapped, being replaced by a more frequent tram service with more stops and a faster service due to the trams' more rapid acceleration. Plans were also announced for a second trial between Rotherham Central and Sheffield at the same time. The Sheffield to Huddersfield plans were later abandoned in September 2009, although the Sheffield to Rotherham route was to go ahead. The initial plan was to use electric vehicles capable of operating on either 750 V DC or , via Rotherham Central to a new station at Parkgate. The scheme was estimated to require £15 million, later revised upwards to £18.7 million to build when first proposed, but was eventually expected to cost £75.1 million. The Rotherham route was originally intended to begin operation in 2015, however this date was put back several times until the October 2018 opening date after a series of delays. Part of the delay was due to the transport secretary failing to approve the building of a 150m (164yd) section of track at Tinsley in a timely manner. The Public Accounts Committee (PAC) was critical of Network Rail's initial estimates for the cost of modifications to the route calling them, "wholly unrealistic". The PAC also noted that Network Rail and the Department for Transport could not provide figures on how much money had been spent on a now cancelled line electrification project. Part of the unexpected rise in the cost of creating the route and the delay was due to the need to demolish and rebuild the College Road road over-bridge next to Rotherham Central station. It was thought that the ballast beneath the railway line could have been excavated to