The evolution of complex engineering systems

Engineering systems are rarely designed from scratch. They are socio-technical engineering systems that evolve over generations of products and policies. This chapter uses tram transportation to illustrate how engineering systems evolve over many decades. A brief comparison between trams in the UK and Germany illustrates that systems that are at one point very similar can develop in very different ways due to seemingly innocuous decisions. The evolution of systems is explained in terms of two concepts, path dependency, which explains how future designs are restricted by decisions taken in the past, and engineering change, which handles the effects of a change on parts of the system and neighbouring systems. To understand the impact of change it is important to model and understand how different elements of a system are connected and how well a system meets its requirements to identify those elements of a system that can accommodate new demands. Different approaches have been developed to manage and predict engineering changes. Understanding and managing change is particularly important for complex engineering systems, which often constitute large-scale long-term investments and are expected to keep operating while the changes are carried out. The chapter concludes with a discussion of how systems can become more resilient to change either by becoming able to absorb expected changes or becoming more flexible in adapting to change