“…In this case, the problem is typically formulated as a multicommodity flow problem Schlechte, 2007, 2008;Caprara et al, 2001Caprara et al, , 2002Caprara et al, , 2006. Further papers deal with a different but related problem, i.e., the problem of inserting additional trains in an existing timetable (Burdett and Kozan, 2009;Cacchiani et al, 2010;Flier et al, 2009;Ingolotti et al, 2004;Lova et al, 2007;Tormos et al, 2008), mostly for scheduling additional freight trains. In this case, the timetable already established for passenger trains is not modifiable, and freight train operators indicate their requests to the infrastructure manager in terms of an ideal timetable.…”