EVALUATING LINE CAPACITY WITH UIC CODE 406 COMPRESSION METHOD: APPLICATION FOR MALATYA-NARLI LINE
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Date
2021-12-01
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Abstract
While demand for railway transportation in Turkey is in increasing trend parallel to the world, the studies to
optimize capacity utilization and allocation has been continuing. This mean that the reliability and quality of
train services should be improved. If the volume of train traffic approaches to the line capacity, these measures
start to deteriorate, and the emerging bottleneck effects are observed along with capacity allocation issues. In
this study, the capacity allocation process in railways is briefly explained and the line capacity calculation
method is presented using a case study. Turkish State Railways (TCDD) has become the infrastructure manager
(IM) since the amendment in 2013. An incorporation named TCDD Transportation A.Ş. has then been
established to operate passenger and freight trains for public benefits. The legal regulation also allows the
private companies to operate trains, named train operating companies (TOCs). These companies demand capacity allocation for trains they would operate according to the regulation. The existing line capacities should
therefore be known beforehand for the allocation. A capacity calculation is exemplified for the single-track
railway line between Malatya and Narlı using the method in UIC Code 406. Mostly freight trains operate on
the line having centralized traffic control (CTC) system and automatic block signal system. For daily capacity
calculation, a line section, which has the longest occupation time by trains, is determined and model trains,
which are representative for similar train groups, are selected. The blocking time stairways of model trains in
the calculation section are established and then the minimum headway times between trains running in the
same and opposite direction are calculated. The blocking time stairways of 47 trains in the order of timetable
are compressed, the total occupation time is calculated as 703.80 min during the day (1440 min), and the mean
headway is found approximately 18 min. This means that the occupation rate of the line is 48.88%. In UIC
Code 406, the recommended additional (buffer) time for the mixed traffic lines is 67%, accordingly the
capacity consumption rate becomes 81.62% (less than 100%). As a result, the existing capacity between
Malatya and Narlı is currently sufficient.
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Keywords
TCDD, UIC Code 406, blocking time stairways, capacity allocation, capacity calculation