The NSTSCE stakeholders have jointly funded this research for the purpose of developing and disseminating advanced transportation safety techniques and innovations. i EXECUTIVE SUMMARY When determining crash causation, crash databases emphasize a single, unitary critical reason (CR) as the primary proximal cause of a safety-critical event (SCE), which leaves no room for the specification of any other potential contributing factors to the crash/event genesis. This is despite the fact that it is well established in the transportation safety field that crash genesis typically involves a convergence of several factors. The aim of this study was to investigate the crash trifecta concept to determine if the convergence of multiple elements, rather than a single, unitary critical reason, has greater value in explaining the complexities of crash genesis. Specifically, the crash trifecta concept is defined as three separate, but converging, elements: 1. Unsafe pre-incident behavior or maneuver (e.g., speeding, tailgating, unsafe turn); 2. Transient driver inattention (which may be driving related, such as mirror use, or unrelated, such as reaching for an object); and