When capacity utilization increases several things happens. On the tactical level, more
trains imply more restrictions when the timetable is constructed, especially if it is a single
track line or a double track line with a heterogeneous traffic mix. As traffic becomes
denser scheduled waiting time, i.e. longer planned travel times, are unavoidable when
more frequent crossings and overtakings are necessary. On the operational level, trains
scheduled closer together increase the risk of secondary delays (knock-on delays) at the
same time as it may also become more difficult to recover from delays.