Here in Vol 2 Oxford Transport Startegy Pg 16.
A longer-term option which would address all these problems would be to tunnel under the city centre, removing the majority of the mass transit operation from street level. New ‘stations’ would be constructed underground, close to the main attractions in the city centre. BRT and bus services could run with ease directly across the city centre, without being impeded by other road users or using indirect routes. Interchanges between north-south and east-west routes would be provided, solving several issues faced by passengers and operators in the existing situation. Whilst the construction cost would be very high (benchmarked costs for similar schemes suggest a capital cost in excess of £500 million), the resulting positive impacts on the public realm, conservation, safety and accessibility would be substantial. We have not yet considered in detail the technical or environmental feasibility of constructing transit tunnels. Clearly, there would be very substantial construction works (and construction risks) and environmental impacts. Within the central core, parts of commercial properties may need to be purchased to allow for street-level entrances to the tunnel stations. If this option were to be explored further, the business case would need to be developed in more detail. This would need to consider the benefits to passengers and reduced operating costs for the service operator(s). Innovative sources of financing would need to be considered, including financing of borrowing costs through departure charges for all services (such as those often used to pay for maintenance or renewal of bus stations).
None starter – but here’s my alternative hair brained plan.
1) Knock down Magdelene College School at the Plain (relocated to edge of City) and use it to intercept in city traffic in South Cambridge not intercepted by edge of city P&R
2) Close the A420 High Street Bridge to cars, buses and cycles/peds only.
3) Place a P&R site/Bus Station at the former Magdelene College School
4) Create a new bus only road across the Cherwell in the short distance between Merton College and Kings Mill Lane
5) Route all buses to the new P&R across the new bridge
6) With the High Street now essentially car free, buses only you create a new on Street bus station just south of Cornmarket to mirror the one at Magdelene Street
7) You dont need to dig under – you intercept all buses before the Cornmarket and there pedestrian walk.
Just think how cities in the Netherlands and Germany would have approached this problem.