I saw this elsewhere and think it is very sensible...
Rules of carriage in Edinburgh
3.2 Travelling with young children
Space on our buses is limited. We recommend that passengers who intend to travel on our services with a small child use a smaller, easily foldable buggy.
Buggies including pushchairs and travel systems which will not obstruct the aisle may be brought onto our buses unfolded. Passengers who board with an unfolded buggy must place it in the buggy space whenever that space is available. If the bus does not have a buggy space, or on buses which have one, the buggy space is not available, one unfolded buggy may be placed in the wheelchair space.
In common with all other passengers, whenever the wheelchair space is needed by a wheelchair user, passengers with unfolded buggies must move to make it available. In order to allow a wheelchair user to board, any passenger occupying the wheelchair space with an unfolded buggy should fold it and place it in the luggage rack. Alternatively, they may choose to get off the bus, in which case a receipt will be issued to allow them to complete their journey on a following bus free of charge.
A Warrant is available to people who cannot fold their buggy because they are disabled or the child in their buggy is disabled. If a Warrant holder shows their Warrant to a driver they will not be asked to fold their buggy. This Warrant does not provide any priority over other passengers when boarding.
Where the wheelchair space and the buggy space are already occupied, additional buggies must be folded and placed in the luggage rack on boarding.
Empty buggies must be folded and placed in the luggage rack.