Using functional analysis to determine the requirements for changes to critical systems: Railway level crossing case study

Level crossings are well known as components of railway networks with the greatest risk of collision and possibly derailment. New technologies have been developed for avoiding collisions, where obstructions on the crossing are detected in time to stop trains from hitting them. The choice to move to a safer system may seem obvious. However, a more detailed analysis of the interaction between the existing level crossing functions and any new retrofitted system reveals that the effectiveness of the system as a whole will suffer unless the new system achieves a particular level of reliability. Analysis of functional interactions in this way will inform the choices of asset owners wishing to upgrade their existing systems.