[bus & coach man]

Strange as it may seem, the actual legal definition is judged by how the passengers have actually paid for the journey. If they pay individually and seperately then it is a bus service. If they pay en block then it is a coach. This raises some very strange situations. If a coach is hired in from a private operator by National express to do a journey to London, then it is a bus. It is legally entitled to use bus lanes within London.
On arrival at London it may then go on to a hire from a travel company to transfer some passengers to an airport. It is now a Coach and as such can only use some bus lanes. i.e. those showing "bus & coach" lane.
This is the police definition, so unless a better one can be found it is the definition I tend to use.