Step 1) Make a jukebox at every interchange / line switch junction, one for each outgoing line from that junction.

Step 2) set each jukebox to lever-activated upon entry to the snitch zone

Step 3) Make the incoming lines pass a series of simple track switches, where "on" = straight toward a stop block, but "off" = turning off on a continuous non-stop path toward one of the valid destinations.

Step 4) Set a group for each juke, that only some random alt is a member of by default. Make them password joinable publicly with name of junction and destination.

Step 5) Hook up jukes to a slow pulse generator then to their respective track switches.

Now anybody who is coming into your town, if they are unaware of this system or haven't done anything, will by default trigger all of the snitches, turning all of them on temporarily and setting all of the tracks to guide them to the stop block where they will have to manually get out and choose their next destination.

However, for savvy people, they can begin wherever they live, and let's say I'm traveling from Breslau to MA to Carbon. I can join the group "CICMACarbon" at the start of my journey. When I get to MA, that one snitch won't flip, and so the track's "off" position will route me fluidly into the Carbon line without stopping, so that I can AFK alllll the way from Breslau to my final destination.

For a multi-segment trip, you could join multiple groups and AFK across the entire map, theoretically.