Equal number of route groups.
East: amdep, brbp, bndep.
West: slbp, hgdep, bbdep, arbp.
Each service may be dual district, east district only or west
district only, depending on the depot(s) which supply the buses.
However, every service has only one major depot/district, so the
service is taken care of by a route group under the major
district.