Quality management is a megatrend at present. This paper describes the systematic search for solutions to problems in bottle-necks of railway systems. Quality management turns out to be the most effective way to gain high throughput. The usefulness is quantified. Quality management of railway systems generally increases revenues, because the required infrastructure is already on hand. In threading only the trains out of schedule cause problems. Delays of a certain magnitude can be compensated by planing the schedule with buffer-times. These buffer-times decrease throughput. A model is used which takes into account technical possibilities and spontaneous disturbances to handle also the trains out of tolerance. The time-distance line is replaced by a time-distance density witch includes and weights all cases. Today's signalling damps disturbances in many cases as shown in simulation. But there are also cases where the disturbances are boosted. Even though these cases are exceptions, they have to be included, because they have major influence on punctuality. Therefore control is required. Diffusion control enhances punctuality less than necessary. As long as disturbance is as big as today, control has no influence. Quality control delivers much better results. If the few trains out of schedule are recognized and kept in the station then the service quality for passengers all things considered is much better than if these trains would disturb the whole system. Capacity is well dealt in publications but measures for quality are missed. The major improvement of the time-distance density in relation to other methods is the complete consideration of disturbance. Therefore stochastic methods are used. A quality measure from view point of passengers is defined. Speed of travel is connected to reliability achieving this speed. The punctuality required to achieve high density traffic is higher than the punctuality asked by the clients. The quality attribute punctuality is not limiting power, as assumed. It is a convincing requirement for high throughput. Capacity and punctuality have been opposite requirements. Buffer-time and spare-time have been used to stabilize delays but they reduce power. This paper demonstrates the possibility increasing power with better punctuality. Over all there is a more profitable use of the railways and a better service quality for passengers. Besides the need of an effective quality management the procedure of planing quality for a railway system is sketched. It is impossible to replace a service product to clients. That is why the goal must be "first time right". The infrastructure required for an effective quality management already exists. This makes this solution tempting. The conclusions are: a) Railway service geared to market requirements needs quality management; b) Quality control at departure-time delivers a better quality level than control measures; and c) High speed capacity asks the highest restrictions to punctuality. (A)
Abstract