Professor Leo Kroon, professor of quantitative logistics at RSM Erasmus University in Rotterdam, describes the task of redesigning the Dutch railway timetable as "rather complex". That is probably an understatement.

Imagine trying to create a system detailing the precise movements of 5,500 daily train services, thousands of pieces of rolling stock and all the personnel needed to run a railway network (a typical day on the Dutch railway involves 15,000 driver journeys). Then figure that, as with a Rubik's Cube, moving any piece of the puzzle could have knock-on effects on another part - meaning that the problem always has to be tackled as a whole, rather than in its component pieces.