Which factors and situations for human functional failures? Developing grids for accident causation analysis

This report describes the work undertaken in Task 5.2 of the TRACE project. Human failures are explained by factors characterizing the state of the system and of their interactions. A grid of factors which could lead to these human functional failures is given along with a grid of pre-accident driving situations. In addition to this, an overview is included of the background work undertaken to establish a methodology for classification of these factors and situations. Factors related to the ‘User’, ‘Vehicle’ and ‘Environment’ are described and classifications for use at a ‘descriptive’, ‘generic’ and ‘in-depth’ level are determined, to allow analysis at different levels of detail of accident data. These factors and situations will be used along with the Task 5.1 functional failures to help identify typical failure generating scenarios in Task 5.3, and the subsequent analysis of real world accident data in other work packages in TRACE. They will also be a useful basis for future improvements in the collection of accident causation data, avoiding the common over simplification whereby road users are seen as the main reason for the ‘failure’ in the accident scenario.