Railway Investigation Report
Safety Issues Investigation Report SII R05-01
Analysis of Secondary Main-Line Derailments and the Relationship to Bulk Tonnage Traffic
In the winter of 2003-2004, a series of train derailments on secondary main lines in western Canada involving broken rails prompted the Transportation Safety Board of Canada (TSB) to initiate this safety issues investigation. To develop an understanding of the factors underlying these occurrences, the investigation examined the commonalities among these occurrences, reviewed relevant TSB data, and used data provided by the railways to test a specific hypothesis.
Subdivisions included in this investigation consisted of those involved with the initial derailments, plus other subdivisions that were selected on the basis of
- track characteristics (that is, secondary main line),
- traffic characteristics,
- geographic location (that is, western Canada), and
- recent derailment history.
Information on rail infrastructure components, renewal programs, testing, maintenance and inspection practices, workforce levels, traffic density, and axle loading was reviewed to establish qualitative relationships among track condition, traffic, defect levels, and derailment frequency. The five-year track geometry and rail defect histories, traffic type and density, derailment history, causes and contributing factors were analyzed to identify potential safety deficiencies. This qualitative analysis of derailment occurrences included both Canadian National (CN) and Canadian Pacific Railway (CPR) data.
Statistical analyses were conducted to test the hypothesis that bulk tonnage traffic, independent of cumulative tonnage, is associated with increased derailment risk due to rail defects. The quantitative analysis was conducted only on CPR subdivision data because an insufficient number of CN subdivisions met the selection criteria either to furnish a sample of sufficient size to analyze or to determine if CN data and CPR data were sufficiently similar to allow them to be aggregated into a single sample.
A statistically significant relationship was established between the incidence of rail defects and the level of bulk traffic. Where rail weight is less than 130 pounds, increased bulk unit train tonnage significantly increases rail defects, resulting in a higher risk of broken rail derailments. This safety issues investigation report identifies risks related to the problems in balancing track maintenance and degradation to the comprehensiveness of the Railway Track Safety Rules and to deficiencies in rail inspection capabilities and maintenance practices.
© Minister of Public Works and Government Services Canada 2006
Cat. No. TU4-18/2-2006E
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