As outlined in the Air Brake Rules and Train Handling Instructions, the dynamic brake retarding force per brake axle diminishes as speed increases. For example, at a speed of 23 mph, the dynamic brake retarding force per axle is 10,000 lbs; at a speed of 40 mph, the dynamic brake retarding force per axle is 5,700 lbs.
engineer] had and the dynamic brakes [he] thought he had working, he could easily have controlled the train down the hill." He further stated that the engineer, based on the information provided to him, could have taken the train down the hill without any dynamic brakes. According to the head-end engineer, based on the information he had, rule 33 did not apply to his train.
The locomotive engineer, the helper engineer, the road foreman of engines, and the general road foreman all testified that they considered rule 61.E.1 to be a recommended general guideline or an option rather than a requirement. Testimony also indicates that engineers have routinely gone beyond the 50 percent reduction. On May 17, 1989, SP issued train order No. 1903, adding the following new rule to their operating rules:
Rule 61.E. Balancing the Grade
Operating freight trains on descending grades involves:
1. Balancing the grade, or holding speed steady at safe and practical values.
The amount of brake (train) retarding force used to balance the grade normally should not exceed one half (50 percent) of the normal full service train brake available if dynamic brake and pressure maintaining are operative.
In order to hold speed steady on a descending grade, the force of gravity must be balanced by the sum of train resistance and brake retarding force. The heavier the grade, the lower the effect of train resistance; and the more brake must be used. Train resistance will vary with the type of cars, train make-up, and train length and weather. On heavier grades the majority of the grade retarding force comes from the dynamic brake and the train air brake.
Within the territories where air brake rule 33 applies, except on Yuma subdivision–Los Angeles division, and with the use of dynamic brake the following brake pipe reductions must not be exceeded to control the train at the following speeds:
Maximum Speed Maximum Air Brake Pipe Reduction 30 mph 13 pounds 25 mph 16 pounds 20 mph 18 pounds