There have been many past studies on leakage, air flow and gradient considerations in the context of the automatic air brake system, and methods used to qualify train brakes. Through a great deal of past research and testing, it was demonstrated that brake pipe leakage, air flow and gradient can impact brake system performance. Many of these past studies were instrumental in determining appropriate air brake test methods, limits and standards still in use today. Recently, the relevance of current air brake qualification standards has been questioned in the context of freight trains operating with technological advancements such as Distributed Power (DP), Distributed Braking Cars (DBC) and Electronically Controlled Pneumatics (ECP). Many of these new technologies enable multiple air sources to be employed at multiple locations in the train so as to assist with brake pipe charging. Making full use of these new technologies may now require a rethink of past standards and practices which, although having served the industry well, were specifically tailored to conventional train operations utilizing only a single air source. The purpose of this paper is to provide a review of the principles governing brake pipe leakage, air flow and gradient, and to examine the possibility of increasing conventional air flow limits for a train operating with either DP or a DBC and thus having multiple air sources. The intent at this early stage is not to prepare a lengthy paper, but rather the goal is to raise awareness, share relevant information and promote dialogue.
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