The recent Phil Jones Associates' "Oxford City Centre Movement and Public Realm Strategy", commissioned by the city and county councils, proposes a radical reworking of Oxford's core in favour of public space and active travel. This offers an escape from the transport "swamp" the city is currently stuck in: the alternative is stumbling along, flailing about but sinking deeper into the quagmire. Everyone concerned about air pollution, congestion and barriers to walking and cycling in Oxford should push the councils to take the proposals in this report, give them flesh, and put them into (respectively) their Local Plan and Transport Strategy.
The details can and will be argued over — the report itself offers two options, of which I think the single one-way loop is more plausible — but the key element is a one-way bus/loading circulation system inside the inner city, freeing up space for walking and cycling in areas such as High St and St Aldates, combined with private motor traffic reduction or removal. The report leaves open the exact form the latter would take, but the most likely approaches seem to be a congestion charge or bus gates. Whatever is done, it needs to be drastic enough to protect the central loop from congestion and to ensure that buses flow smoothly even in peak hour; and it really needs to break the "tragedy of the commons" in decisions to drive into or through central Oxford instead of using buses. A complicating factor is that some of the space needed for walking and cycling has to come from space currently used by buses, which will then take some of the space currently used by private motor traffic.
I think it's now clear, even to conservative councillors, that something drastic needs to be done: currently pedestrian comfort and even safety are compromised, cycling through large parts of the city centre is unthinkable for half the population, congestion hurts employees and employers and residents (through inflated housing costs and shortages of teachers and nurses), and air pollution is poisoning everyone. Given the constraints on space — and Oxford really does have narrow medieval streets! — simple physics means the only possible way to get increasing numbers of people through and into the city (and to allow them space once there for visiting shops and seeing the sights) is to shift them from the least space-efficient transport mode — cars — to walking, cycling, and well-utilised bus services. Similarly, space currently used by parked cars needs to be repurposed for bus layovers and bus passengers, bicycle parking, and space for people.
The key gains are a vastly greater "public realm", with space not just for pedestrians going somewhere but for people to be, to appreciate being in Oxford without worrying about cars or buses. This is most clearly seen in the outcomes for High St and St Aldates, which will have broader pavements and separate cycle tracks, but there would be improvements across the centre, in noise and pollution reduction as well. Cycling around or across the city centre will become feasible for the frailer and less confident, though the full gains from this would require cycling infrastructure to be improved on radial routes into the centre as well, perhaps along the lines proposed by Andrew Gilligan. The health benefits of reduced pollution and increased walking and cycling would be immense.
Now some compromises need to be made in any change this drastic, and everyone will dislike something about it, but "no one worse off" Pareto-optimisation (more often implemented as "no car driver worse off" optimisation) has reached its limits. Running buses down Holywell St may diminish the heritage value there, but if that proves necessary it needs to be set against vast improvements on High St and elsewhere, where it might become possible to stop and admire the buildings without being taken out by a bus or pushed off an overcrowded pavement by the throng. A reduction in motor vehicle access may hurt some businesses, but gaining better pedestrian and cycle access will (based on evidence from elsewhere) more than offset that for most, and certainly for property owners. Some bus routes may become longer, but they will also be much less congested than they are at the moment and there should be better provision for layover space. Some bus passengers may have to walk further to reach bus stops, but there will at least be room at the bus stop for them to wait — and the walk should be vastly more pleasant and possibly even faster. Some die-hard vehicular cyclists may miss weaving around the buses and sprinting with taxis, but they should get cycle paths so good that they won't mind sharing them with eight year olds.
If these trade-offs seem ok to you, and you think Oxford should have a pleasant, healthy, sustainable, and attractive centre, then mention your support to for this proposal to your councillors. And be prepared for a fight — change on this scale is going to create a backlash.
I also think the Gilligan report on cycling in Oxford is fantastic, but it doesn't really address the inner city at all.
Reworking central Oxford along the Phil Jones lines would be a complement to these, not an alternative. It would provide a way for people on Gilligan-style routes to get into or through the centre. It would also drive general motor traffic reduction across the city, allowing space to be reallocated to cycle paths and junctions to be redesigned for the safety and comfort of people walking and cycling, and allowing rat-runs to be filtered.