Multi-train simulation: verification and accuracy

Many simulation packages model the movement of individual trains, to establish the speed profile, or support timetable planning. Some extend the potential of simulation to model multi-train operations by adding data on the network infrastructure. Extra functionality is achieved by increasing the range of input factors. A single train simulator will match train mass with tractive effort to calculate train acceleration. Multi-train simulation needs detail of signal section lengths, the track layout and locations of critical track circuits. Validity is improved by further additional input factors, such as gradients, train resistance, transmission efficiency, equipment and driver reaction times, and specific signalling rules. However, comprehensiveness brings difficulties. A package capable of detailed simulation will be complex and data-hungry. Operators must be trained.. their knowledge must be used regularly or lost. Model-building will be expensive, and elapsed time possibly prohibitive in practice. Input errors may obscure genuine effects. Preparing and using the model also needs knowledge of traction, signalling and interlocking, and understanding of timetabling. The skills will rarely be found in one individual, but require a pool of users, increasing the ongoing workload needed to support the activity. Moreover, each data item brings with it some uncertainty. Where new input opportunities extend into data areas that are poorly researched or intangible, values may be estimated or guessed, and added uncertainty mask the added validity. This is particularly true where human behaviour is involved. Network simulators are ideal for specific and well-defined tasks, but for "high level" applications detailed input is immaterial. Comreco Rail Ltd. has risen to the challenge of offering a simulator that minimises the workload input, avoids reliance on specialists, and offers results within the timescales of management decisions, by adding simulation functionality to the TrainPlan timetable management system.