This thesis describes the developement of a new type of simulation tool for the assessment of designs of public transport facilities (stations, airports) and other public spaces with intensive pedestrian flows. Since the available space for such facilities is increasingly under pressure, the space efficiency and walking comfort is becoming more and more important. The developed simulation tool provides designers and decision-makers with all kinds of quantitative information about the expected quality of pedestrian (traffic) flows such as travel times, waiting times, queue building, preferred routes, visits to shops and counters, etc. This information is very useful in comparing multiple designs as well as to optimise a specific design. The simulation model also is meant to improve schedules of public transport services at interchange nodes by minimising passenger transfer times. To that end, special attention is paid to the modelling of boarding and alighting processes. New insights about walking have been gained by performing unique large-scale laboratory experiments in which large groups of subjects were assigned various walking tasks, such as high volume crossing flows and walking through bottlenecks until flow breaks down. Specific walking and route choice models are developed using observations of passengers on platforms (such as in Delft) and route choice through the station (such as in Delft and Breda). The tool has proven its value in the analysis of new designs of the future Rotterdam Central Station and performance tests of the new Breskens-Vlissingen ferry terminals.