There is no light bulb solution to this problem. Cities that attract large numbers of tourists to their historic centres find themselves trying to reconcile conflicting needs. Tour operators who are on a tight schedule (the average stay-over for coach borne tourists in Bath is said to be 90 minutes) want to get their customers into the popular locations and out again with as little fuss as possible. Then it is on to Stonehenge and Longleat. Cities on the other hand, and particularly residents who live in the historic core, want to reduce as far as possible the nuisance associated with tourist coaches such as congestion and in particular harmful emissions.
The standard model to which many cities aspire would have visitors dropped off at designated points as close as possible to the central zone and picked up again at pre-arranged times as coaches return from dedicated parking areas further out. This model has obvious failings. Each bus makes two visits to the city centre thus disrupting operators' schedules and increasing congestion.
An obvious improvement would be in effect a park and ride system for coaches. All coaches park outside the centre in dedicated parking areas and shuttles carry visitors into and out of the centre. The electric 'petit trains' and shuttles operated by such French cities as Montpelier, Nimes and Toulouse which are 'themed' as part of the visitor experience and provide direct access even to traffic-free streets could easily be adapted for this purpose. Of, there would be numerous problems associated with trying this in Bath including the usual issues of land, routes and resources. Perhaps the river could be brought into use. It is vital that BANEs get specialist advice on addressing this issue sooner rather than later.