I have the idea to make the S-Bahn Frankfurt to the line with more tunnels. S4 Frankfurt (Main) Südbahnhof to station Kronberg (Taunus). And s5 from Frankfurt Südbahnhof to Friedrichsdorf station and players can change trains from s4 to s5. These are German trains for these lines (BR 423) (BR 430) and (BR 420). I hope this add-on will be available soon for Train Sim world.
