Railway Track & Structures - December 2008 - (Page 36)

Optimizing winter speed restrictions Optimizing winter speed restrictions To optimize cold-weather speed restrictions, Canadian Pacific Railway worked with NRC Canada to nvestigate and recommend an alternate approach. by Yan Liu, Chris Ladubec, Jon Preston-Thomas and Eric Magel, Centre for Surface Transportation Technology, National Research Council of Canada, and Michael Roney, Canadian Pacific Railway T he experience of the Canadian Pacific Railway is that the probability of breaking a rail increases significantly under conditions of extreme cold. When the ambient temperature drops below -25ºC (-13ºF), CPR has a practice of limiting the train speed, with the goal of reducing impact forces from shelled and out-of-round wheels. Under the current approach, trains are generally slowed down to 35 mph in site-specific track segments (those that in the recent past have experienced cold weather breaks, have lighter rail sections or have support problems that make them more susceptible to cold weather breaks) at temperatures of -25ºC and colder. Then, at temperatures of -35ºC (31ºF) and below (-30ºC for some subdivisions), train speeds are generally limited to 35 mph in all track segments in the subdivision. The current policy, while effective, has a substantial impact on average train speed. CPR believes there are opportunities to better optimize cold-weather speed restriction rules through the application of good science and contracted with the National Research Council of Canada’s Centre for Surface Transportation Technology (NRC-CSTT) to examine the problem and recommend an alternate approach. NRC-CSTT chose to look at the issue as one of “stress versus strength,” following the popular “stress state of the railway” approach initiated by the AAR. “Stress” refers to the loading that the track components see due to environmental conditions and railway wheel contacts. These stresses tend to be higher in winter because of the Figure 1, top left: Frequency Distribution of WILD Impact Measurements–Linear Scale. Figure 2, top right: Temperature Dependency of the maximum WILD readings for each train, winter vs. summer. www.rtands.com 36 Railway Track & Structures December 2008 http://www.rtands.com

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Railway Track & Structures - December 2008 Contents On Track Industry Today Supplier News AREMA News NRC News TTCI R&D Hand-Held Tools Continue Big Role in Railroad Engineering AREMA C&S Moving Ahead Optimizing Winter Speed Restrictions RTA 2008 Conference Makes Splash in Savannah, Ga. Products and Literature People Calendar Sales Representatives Advertisers Index Website Directory Professional Directory Classified Advertising Chicago Perspective

Railway Track & Structures - December 2008

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