Mannheim sits alone cut off from Heidelberg even as a Rhein-Neckar extension out of Heidelberg is announced ! Worse, the big regional news in Germany in summer 2025 was the reworked Riedbahn, so-called, from Frankfurt south to Mannheim. Not having Frankfurt am Main connect to Mannheim is as weird as our isolated Hamburg, or non-existant Berlin, not to forget that Würzburg and Achaffenburg sit disconnected from each other. Just look at Heidelberg north to Weinheim ... a very busy run, but completed as Heidelberg to Darmstadt, from which city so many options flow to finally connect a regional network. The biggest issue for DB in 2025 ? Hamburg to Berlin !
