The Danube-Iller Regional S-Bahn (Regio-S-Bahn Donau-Iller) is a "regional" S-Bahn system in the Ulm and Neu-Ulm area. It operates Regionalbahn services on electrified and non-electrified lines. Its core is Ulm Hauptbahnhof, which acts as a hub between the regional S-Bahn (RS) lines, other regional services and long-distance services.[1][2][3] In December 2020, the first two RS lines from Ulm to Memmingen (RS 7) and Weißenhorn (RS 71) were put into operation in the Bavarian part of the Danube-Iller planning region (Region Donau-Iller). When the 2021/2022 timetable changed, three more lines followed in the Württemberg part of the region on the southern railway to Biberach (RS 2 and RS 21), on the Danube line to Munderkingen (RS 3) and on the Brenz Railway to Aalen (RS 5 and RS 51).[4] Further lines are to be added in the following years. The network is expected to be completed by 2030.[5]
The Danube-Iller Regional S-Bahn is administered by the Donau-Iller-Nahverkehrsverbund GmbH (DING, "Danube-Iller local transport association") and two neighbouring transport associations, the Heidenheimer Tarifverbund ("Heidenheim tariff association") and OstalbMobil ("Ostalb Mobile").