Too much emphasis is placed on suburb to center city terminal, not that it may be needed, but it is just a part of the traffic flow. Fortunately, in recent decades the transit authorities recognized some 'reverse' commuting that is traffic oriinating in city centers to suburb work. Still not much in way of suburb to suburb routing either from one side of an urban area to opposite side, or along the arcs that have formed along the ring roads we have built.
Ring roads have been around a while. In Pittsburgh, ring routes were marked by Allegheny County using existing roads [a lot of 2 lanes] by 1952, to avoid going through downtown to get from one suburb to another.
I was in Chicago area in 1994 at a rubber convention downtown, I proceeded out to Wheeling where our parent firm was using Northwestern {Metra] to Palatine and PACE to Wheeling. PACE did not particularly impress me I am sorry. I got a ride to the Northwestern station at Arlington Hts to return downtown. In other trips to the parent firm, I would fly into O'Hare on the first plane from Cleveland, get a rental, and drove up Des Plaines Road and did about as good time as they did on the jammed freeways.
IIRC, they were looking at a ring routing for Metra, but that must have been passed over. I do not recall what happened.
Here in Northeast Ohio, someone once in a while tries to get people interested in a commuter train to downtown Cleveland, but that is not where a majority of traffic going to. It is going across Cleveland or around the 271-480 beltway. Laketran [Lake County] runs some park n'ride to downtown during rush hours M-F with some transfers to Greater Cleveland RTA.