The interaction between driver mental and physical conditions and errors causing traffic accidents: An analytical approach

An analytical methodology was developed to study the relationships between driver behaviors causing and immediately preceding an accident (Direct Causes), and accident causal impairments in drivers' predisposing mental and physical states (Indirect Causes). A statistic defined as the Relative Involvement Factor (RIF) was developed to reflect the change in the likelihood of any direct accident-causing behavior being implicated given the existence of a causally relevant mental or physical impairment. The usefulness of the RIF was demonstrated in an analysis of 420 traffic accidents. The analysis indicates that causal conditions and states suppress certain direct causes while increasing the likelihood of others. Specific relationships are discussed.