When planing your routes, one think you need to keep on your mind. Agents/sims goes from home (green) to some other color district, then back to home. Their route always start in green, their route always ends in some other color. The green district has highest concentration of travel hungry people.
Single ring line around the city – agent travels from home to the destination by bus, but there is no way back. So he walks.
Double ring line(clocwise-anticlockwise) around the city – agent could travel back and fort by bus. If the an agent would use the big cicrle line line from green to red like :green-green-green-blue-blue-red he probably go by walk/car cose so many stops are slow.
Inner city transport should be considered as a feeder to your trains. If you want to take care about all people who go from home-green to the local shop-red you would loose money.