Optimizing Winter Speed Restrictions

This article describes research conducted by the National Research Council of Canada's Centre for Surface Transportation Technology (NRC-CSTT) on optimizing cold weather speed restrictions for trains. Initiated by Canadian Pacific Railway (CPR), the study looked at the issue of limiting train speed when extremely cold weather would increase the probability of rail breakage. Researchers examined the issue from a "stress versus strength" perspective in which stress refers to the track components load resulting from environmental conditions and railway wheel contacts, while strength refers to the track and infrastructure's ability to endure forces, withstand damage, and avoid breakage. Using a stress model and Wheel Impact Load Detector (WILD) data, researchers analyzed nine track subdivisions. A strength model was developed using defect data representing different types of defects/service failures. A Stress versus Strength Model was then developed and incorporated into a software tool known as the Trains Highball All Winter ((THAW) meter which provides the maximum recommended speed for an individual train in cold weather. Factors taken into account by the THAW meter include the subdivision, ambient temperature, and train wheel condition.