North American freight train length has increased over the past 20 years to take advantage of the economies of scale they offer. In addition to these economic benefits, it is important to understand the safety of longer-train operations. Previous theoretical work suggested that operation of fewer, longer trains might improve safety. However, due to the lack of detailed, fine-grained data on train operation by train length, past studies faced challenges developing suitable exposure data needed to investigate the possible relationship between train length and derailment rate.