Freeway Speeds and Speed Variations Preceding Crashes, within and across Lanes

Relationships between speed choice and crash occurrence have been difficult to identify. This work examines vehicle speeds (and their variations) derived from single loop detectors for several Southern California freeways, within and across freeway lanes, together with corresponding crash data. While a variety of factors clearly influence speed and speed variance, there is no evidence in these crash data sets, and observations of their corresponding series of 30-second traffic conditions, that speeds or their variation trigger crashes.