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Home > Zurich dispatching center > Tools > Time-distance diagram > Forecasting trains Forecasting how a train will runAssumptions for the forecast In creating the schedule, SBB takes a train's technical running time and adds 7% to it. When a train is running behind schedule, the dispatching system presents a forecasted run for the train that assumes the train will run at its technically maximum speed until it has returned to schedule, and thereafter at the somewhat lower scheduled speeds. When a train is running ahead of schedule, the dispatching system assumes the train will continue to run with its scheduled speeds between measurement points. Sources of error in the forecast Such estimates are subject to error, especially in the case of freight trains. Also, the dispatching system's projected speeds take no account of sections with slow speed limits due to work projects, as in the following examples:
Taking into account slow sections Taking into account such sections in speed forecasts is theoretically possible, but very complex to do with any accuracy, especially because trains tend to bunch in a queue at the entry of slow zones, and the third train that follows two others sees yellow signals and therefore slows down earlier. Dispatchers must therefore use their judgement in taking these delays into account, as the dispatching system does not do so when it forecasts the train's progress on the dispatcher's time-distance diagram. On the time-distance diagram, the dispatcher can manually move a train's forecast line either downward, in other words to indicate the train will run later than the dispatching system has calculated, or upward, to show earlier running. |
This site was originally assembled in March 2001. Comments are welcome. Copyright © 2001-2005 George B. Raymond, Jr. Disclaimer |