Bristol is considering constructing a new underground metro rail system that could cost up to £4bn.
A draft transport strategy reveals the city is considering lightweight underground systems, such as the Automatic Light Vehicle systems used on the continent in Turin and Lille as well as other places around the world, in partnership with officers at the West of England Combined Authority (WECA).
The metro plan is part of wider transformational transport schemes being considered as it seeks to deal with its major congestion problems.
The city said there was a funding gap of £10bn to deliver the transport schemes and has discussed a congestion charge, a workplace parking levy, business rate supplements and council tax precepts to help raise cash.
Initial feasibility work is already underway for the Bristol metro plan to explore areas such as construction and operation costs, ground conditions, patronage forecasts, future trends, and other considerations.
Bristol transport officials suggest that due to 'the restraints on many of our corridors, in many cases, the only deliverable alternative is to go underground'.
The new metro service would have three lines and would be fully automated and thus need no drivers. The ambitious scheme would take around 20 years to deliver.
'A light automated metro could be transformational for the region, cutting peak journey times from Aztec West, Emerson’s Green, and the Airport to the City Centre to under 25 minutes, with increased capacity and reliability with services every couple of minutes,' the draft report states.
'An underground system would enable the removal of some above ground infrastructure, and streets could be redesigned to improve the public realm. While an underground system is technically deliverable, the costs are significant, at around £3-4bn needed for three lines.'
A detailed combined authority joint transport plan 2036 is due for publication in October.
A feasibility study is currently underway on implementing a Clean Air Zone in the city, which could include a charge for vehicles.