The purpose of this study was to identify probable causes of and factors responsible for accidents occurring at railroad crossings protected by gates. Two important goals of this study were to (a) compare the results obtained for the two types of warning systems activating the gates: fixed distance and constant warning time systems, and (b) test the hypothesis that extended, or widely variable, warning times create a lack of credibility in warning signals. These objectives were achieved by statistically analyzing accident data obtained from the National Rail-Highway Crossing Inventory and the Railroad Accident/Incident Report files for the period 1975 through 1984. An accident classification by circumstance (movement and position of the car in relation to the tracks and the trains) highlighted some causes and factors responsible for the different types of accidents. The classification indicated results and led to the development of a similar interpretation of the accidents for both types of warning systems. Further analysis confirmed and quantified the small impact of environmental factors (bad weather, poor visibility at crossings, etc.). Trends found in relation to warning times tended to indicate that lack of credibility in warning signals was a factor in the accidents.