Author: Milton R. Johnson

Date of Publication:  November 1984

Sponsoring Agency:  U.S. DOT - Federal Railroad Administration

Performing Organization:  IIT Research Institute

Report No: DOT/FRA/OR&D-84/16

Abstract:

An evaluation has been made of how certain characteristics of the modern freight train braking system affect the safety of train operations. The parameters considered included, net braking ratio practices, the frictional properties of brake shoe materials and dynamic brake rigging efficiency factors. The questions of whether or not safety would be enhanced by obtaining shorter stop distances for freight trains was also addressed and possible techniques for improving the characteristics of freight train braking systems have been identified. Stop distances could be reduced by increasing braking ratios on loaded cars, but a variable capacity brake would have to be used. A major effort was directed toward understanding the factors which lead to severe slack run-in and run-out effects by predicting shock motions and peak coupler impact forces under various con-ditions. Based on the results of these analyses, an increase in loaded car braking ratios beyond current practices is not recommended unless steps are taken to mitigate the development of slack action effects. Two possibilities are the use of a method for simultaneously applying the brakes on each car in the train and the reduction in the inter-car clearance.
 
 

No. of Pages:  107