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Pages 9-21

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From page 9...
...   1 LETTER REPORT ON A REVIEW OF THE DEPARTMENT OF TRANSPORTATION TESTING AND ANALYSIS RESULTS FOR ELECTRONICALLY CONTROLLED PNEUMATIC BRAKES INTRODUCTION The U.S. Department of Transportation's (DOT's)
From page 10...
... 2 According to DOT, ECP brake systems reduce the time before a unit train's pneumatic brakes are fully engaged and therefore are more effective than other pneumatic brake systems. After confirming a need, ECP brake systems simultaneously send an electronic braking command to all equipped cars in the train.
From page 11...
...   3 BOX 1. Overview of DOT's Modeling and Analysis Approacha "By working with Sharma, FRA [the Federal Railroad Administration]
From page 12...
... 4  Calculate the benefits of ECP brakes on a curved track that is representative of the distribution of curves on the rail network.  Analyze alternative derailment initiation events (such as broken rails or broken wheels)
From page 13...
...   5 BOX 2. Committee's Phase 1 Findings and Recommendations Concerning Brake Force Propagation in Emergency Applications 1.1.
From page 14...
... 6 BOX 3. Committee's Phase 1 Findings and Recommendations Concerning Ensuring That the Testing and Analysis Are Focused on the Significant Factors 2.1.
From page 15...
...   7 DOT's ANALYSIS AND TESTING RESULTS On July 6, 2017, DOT presented the results of the analysis and testing conducted in response to the committee's Phase 1 recommendations.11 The status of other items in DOT's plan that were not specifically addressed by the committee's recommendations is provided in Appendix F Brake Force Propagation in Emergency Applications In response to the committee's recommendations on brake force propagation in emergency applications (see Box 2)
From page 16...
... 8 Associates for a 100-car train (all DOT-117 tank cars) with a derailment initiated between the locomotives and the first car in the train.
From page 17...
...   9 DOT provided the following reasons for changes in the likely number of punctures:  A more realistic brake propagation estimate for conventional pneumatic brakes led to a decrease in the estimated number of punctures. Previously, the maximum brake cylinder pressure buildup time allowable by AAR standards had been used in the analysis.
From page 18...
... 10 in DOT's original approach. DOT indicated that the rest of the variation in derailment damage is attributable to unpredictable factors.
From page 19...
...   11 ties. For example, DOT indicated that 0.67 seconds is the amount of time after derailment initiation for ECP brakes to apply.
From page 20...
... 12 length) is the result of varying model input parameters: lateral failure load of the track, ground friction value, and lateral force used to initiate the derailment.
From page 21...
...   13  There was no detailed vetting process of the model simulations by outside experts who were given enough data and asked to replicate independently the DOT–Sharma results. The outside experts also could have examined in detail the LS-DYNA input files that DOT–Sharma used.

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