In railway operations research several approaches exist to validate and analyse the consequences of infrastructure and/or timetable changes. It is possible to classify the used methods into analytical, simulative methods or design-engineering. The appropriateness of an approach depends on the actual situation. The software tool LUKS combines all three approaches.
Analytic methods
Analytic methods are applied to perform a long- to mid-term appraisal of infrastructure variants. In general, the exact timetable which has to be faced by the infrastructure is not yet known in this situation. Instead, by means of queueing theory the operating programme is understood as “customers” wanting to be “served” by the infrastructure. This way, the capacity assessment is directly linked to the operation’s quality expressed in terms of scheduled and unscheduled waiting times. These performance indicators can be calculated for different parts of the infrastructure, which is decomposed into “servers”:
- Lines
- Stations heads (“gril”)
- Serial route nodes
The usage of aggregated train types instead of an exactly given timetable allows a very quick setup, since there’s no need to compile the entire timetable for each infrastructure variant. Futhermore it permits the modelling of yet uncertain constraints (e.g. knowledge on the number of trains). [details]
Simulative methods
Simulative methods should be applied to perform mid-term to short-term evaluations with comprehensive consideration of constraints. Two modes of simulation have to be distinguished:
- Simulation of timetabling: The practicability of timetabling(!) for a given infrastructure is evaluated by an asynchronous simulation approch. As an input parameter, a rough train-path order needs to be given in advance.
- Simulation of operation: The operation’s quality for a given timetable and infrastructure is evaluated by disturbing operating by primary delays.
In both cases the input parameters of a simulation can be easily derived by “enrichment” of analytic scenarios. [details]
Deterministic methods (design-engineering)
Design-engineering is the appropiate approch for a profound evaluation of the correlations between an exact given timetable and the infrastructure. It permits a proof of feasibility of a timetable with consideration of additional constraints (e.g. train intervals, connections, turn-arounds).
A second field of application is the timetable-dependent compression according to UIC Code 406 (e.g. to detect, which share of capacity is bound by “grandfather” contracts). [details]
