The Interregio-Express is a local public transportrailway service operated by the Deutsche Bahn which is only available in the German states of Baden-Württemberg, Bavaria, Saxony, Saxony-Anhalt and Berlin as well as in Switzerland. The IRE service was first introduced in the 2001 summer timetable, due to the increasing abolition of Interregio routes by DB's long-distance division. As a result, several German states ordered InterRegioExpress trains on the routes affected. In addition IRE trains were also introduced on routes that had not previously had an Interregio service. Unlike the former Interregio trains, IRE trains were classified as local passenger trains and can therefore be used by passengers with local tickets. This led however to passengers being irritated, especially to begin with, because they frequently did not realise that they could use these trains with local tickets. Furthermore, the new train type was often wrongly referred to in the early days as an InterRegionalExpress or ironically as an InterRegioErsatz. However, since then the name Interregio-Express has established itself.
In the meantime IRE trains with former IR coaches ran on the Saarbrücken–Kaiserslautern–Ludwigshafen–Mannheim route for a year, a route now worked by the more usual Regional-Express services. In Hessein 2001 differences arose between the DB AG, which designated inter alia the Frankfurt–Gießen–Kassel and Frankfurt–Gießen–Siegen as InterRegioExpress routes, and the RMV, which steadfastly refused to adopt this new train category and even today uses the defunct StadtExpress term. In addition, in several federal states, on the introduction of the InterRegioExpress, former RE routes were changed to IRE routes. Whilst the difference between IRE and RE is hardly discernible, RE and RB trains can clearly be told apart just by the frequency of stops. The renaming of RE to IRE has been reversed in all cases.
IRE services in Baden-Württemberg use a great variety of stock, including diesel-driven tilting trains of classes 611 and 612, double-decker coaches of various generations and locomotive-hauled trains with n coaches. In earlier years y coaches could also be seen as IRE trains as well as DBAG Class 650 multiples. Moreover, until spring 2006 old Class 112-hauled Interregio coaches in classic blue livery were also used on the Karlsruhe–Pforzheim-Stuttgart line as IRE trains. The delivery of newer double-decker coaches and Class 146locomotives however means that that type of train formation belongs to history. Class 612 diesel-powered tilting trains are used on the Franconia-Saxony Express.
