This report analyzes factors contributing to bus operations safety incidents at TriMet, the transit provider for the Portland Oregon metropolitan region. The analysis focuses on 4,631 collision and non-collision incidents that occurred between 2006 and 2009. Empirical analysis of these incidents draws on a wide array of operator-level data recovered by transit ITS technologies in combination with information from TriMet’s human resources, scheduling, and customer relations databases. Incident frequencies are estimated in relation to operators’ demographic characteristics, employment status, assigned work characteristics, service delivery and performance indicators, temporal factors, and customer information. Apart from identifying factors that are empirically related to the frequency of safety incidents, the findings offer insights into operations policies and practices that hold promise for improving safety.