Before around 1970, when PTEs absorbed many municipal operators and the National Bus Company reorganised the territorial companies, routes shared between three or more operators were common. This was prevalent in South Wales and Lancashire/Manchester, where many interurban routes were shared by the municipal operators of the terminus towns, the local territorial company (such as Ribble or Western Welsh), and possibly another municipal from an intermediate town. The most operators I've found for a route is four. Route 292 Bury-Rawtenstall-Water (on the excellent Timetableworld website) was joint between Ribble and three municipals: Bury, Rawtenstall, and Ramsbottom UDC. Route 320 from Liverpool to Wigan was shared between Ribble, Lancashire United Transport, Wigan Corporation and St Helen's Corporation. I don't know if Liverpool City Transport was involved to make five. Does anyone know of other bus routes which were shared by four or more operators, for example the long routes through South Wales valleys to Cardiff and Newport? I'm interested in local bus routes, not the pooled coach services such as between Lancashire and Blackpool, or Liverpool to Newcastle.