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[quote user="tree68"] [quote user="Bucyrus"] Regarding the “right answer” to the question of how many handbrakes are necessary, semantics enter into the answer.  Both of the following conflicting answers are true:   1)      There is no “magic number” or accurate rule of thumb, guideline, chart of information, or accurate means to calculate the proper number of handbrakes required.  Under those terms, it is impossible to know the number, so it is accurate to say that there is no number. [/quote] Not entirely true - the way to determine the number of handbrakes necessary is to test.  I would suggest that your statement be changed to read "...it is accurate to say there is no predetermined number for a given situation."  That there are guidelines in the rules/timetables says that as the result of experience/testing/scientific calculation, the number has been determined - so there is a number. [quote] 2)      There is a specific minimum number of brakes necessary.  One less than the minimum, is too few.  [/quote] This statement is true.  Once again, however, determining what that minumum number is is best done by testing. [/quote] I agree that the test is intended provide the required information to know the minimum number of handbrakes needed, but my item #1 was meant to exclude the test.  That is why I stipulated “Under those terms, it is impossible to know the number.” My item #2 requires the test. I made the distinction between item #1 and #2 because it seemed to be the basis of considerable disagreement here yesterday.  My point is that two conflicting interpetations are true. But looking only at the push-pull test:  Paul North’s previous post brings up several questions that could cause the results of the push-pull test to vary.  Also, the Canadian TSB states that the test is unreliable in mountain grade conditions.  And to reinforce their viewpoint on that, they are immediately making the need for the push-pull test obsolete for trains handling dangerous cargo.  They stated their finding that the push-pull test was unreliable in 2009.  They said that when using the push-pull test in mountain territory, it was impossible to determine whether the amount of handbrakes set complied with the company’s requirement that the number be sufficient to prevent the train from rolling with air brakes released.
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