Bern is the centre of the , which covers the cantons of Bern and Solothurn and includes the towns of Biel/Bienne, Solothurn, and Thun. The network allows easy and coordinated travel on all modes of public transport, such as trains, PostAuto buses, trams, buses (trolleybuses and motorbuses) and others, regardless of transport operator. Fares are based on the number of zones in a journey. The central part of Bern, (excluding Bümpliz, ''Betlehem'', ''Bottigen'', ''Brünnen'', and ''Riedbach'' in the west of the municipality), is part of the fare zone ''100''.