CWA OF RAIL LEVEL CROSSING SYSTEMS
As outlined in Chapter 2, CWA (Vicente 1999) is a systems analysis and design framework that has previously been used both to analyse sociotechnical systems and to inform system design or redesign activities (see Bisantz and Burns 2008, Stanton et al. 2017). The framework describes the various constraints that influence behaviour within systems, with design applications often focussing on making system constraints visible to operators in a way that supports them to adapt and respond to unexpected situations and system disturbances. Another notable feature of the framework is that it is formative in nature, with its methods able to describe both how behaviour currently occurs (descriptive analysis) and how it could occur given the systems constraints, or with modification to these constraints (formative analysis). This formative component is especially useful for informing system design or redesign, as it enables consideration of different ways in which functions and affordances can be achieved.
The CWA framework comprises five analysis phases (Vicente 1999). In this application, only the first four phases (Work Domain Analysis [WDA], Control Task Analysis [ConTA], Strategies Analysis, Social Organisation and Cooperation Analysis [SOCA]) were employed. The fifth phase, Worker Competencies Analysis, was not applied as it was determined that the outputs from the first four phases provided a sufficiently in-depth account of rail level crossing systems to identify the areas of sub-optimal functioning and provide insights to inform redesign. Full details of the analysis are available in the work of Salmon et al. (2016b); a summary is presented in this chapter.