While I am not attempting to refute anything said here, I will give examples from my career on the ground as to why I do not agree "dumping the train" is the ultimate way to secure a train.
1. Chatham, NY on Conrail's Boston and Albany Line. We stalled eastbound on train SELA (Selkirk to Lawrence). We were ordered to leave our rear 60 cars, and take our head 50 cars 24 miles east to Pittsfield, Ma. The STO lived nearby and came to give my a hand. After I made the cut on the cars to be left, he asked how many hand brakes I was going to apply. I told him at least 30. He looked surprised. I told him at least 30 of the cars were loaded with grain for Prince Spaghetti. I explained in my experience, any time you had a block of cars associated with unit trains (coal, aggregate, grain, etc), the control valves would get gummed up and that cars would bleed off after an emergency application. He still looked surprised, but I quoted the "need to apply a sufficient amount" verse, and said I didn't want to hear about cars that rolled westward and stopped in Chatham Center blocking the crossings.
Off we went to Pittsfield, made our drop, and followed Amtrak 449 back to Chatham. In the hour and a half it took, 18 of the grain cars had bled off, and 5 cars of the other block had bled off.
2. Tompkins Cove NY on Conrail's River Line. Dropped 101 coal hoppers at the plant. Took the engines south to Kearny, NJ for servicing. Got out on our rest out of the hotel for a northbound trip up the River Line. Followed a train at restricted speed and was able to look at the train we left there 15 hours earlier. At least 20 of the hoppers had bled off.
3. Trap Rock, Ma, (west of Springfield, Ma.) Dropped 40 Conrail ballast hoppers on tracks 3 and 5. I wound on 25 handbrakes, as there is a grade. I spoke to the operator who loaded the cars a few weeks later. To reposition the cars for loading he said all he had to do was take off about 5 handbrakes and the cars began to roll. Usually he had to bleed them off and use his front end loader to push the cars.
I'm sure others who have worked T & E can cite other examples. I can easily think of more. However, from a technical / operational side, I can say why I didn't want a train to be dumped as a means of securement if I was going to recrew it.
First of all, it takes on average 1.25 minutes per car to fully recharge the air system and reservoirs following an emergency application. So for a 100 car train, that's roughly 2 hours. If I'm the conductor responsible for putting the air back to the train, I'm concerned. As the trainline charges, the brakes will release. I'm concerned whether or not the handbrakes that were applied will hold the train, especially if parked on a grade. Because at this point, the handbrakes and/or the tractive effort of the locomotives will have to hold the train in place. You can't apply the air brakes, because there are none at this point. Not a comfortable feeling.
Secondly, I'm concerned with how long the train has been left off air. When I swung a lantern, if a train was off air for more than 4 hours, a new Class 1 brake test had to be performed. For those not familiar with a class 1 air test, it is basically the following: charge train to within 15 lbs of setting on locomotive air brakes. (Most freights works on 90 lbs of pressure) So when the gauge on the rear reads 75 lbs or above, someone makes a 20 lbs reduction in the air line. Someone walks the train (both sides) to verify brakes apply on every car. (I'm leaving out the leakage test) Once determined brakes apply on every car, you have to verify the release. This can be done by walking the train again, or by means of a "rollby" inspection...you remain stationary while the train is pulled by you.
In other words, it is a time consuming process. And on a railroad one person crews, I'm not even sure how it would be done.
As I stated before, I am not attempting to refute anything. My sole point was to provide a perspective from someone who has had to secure, recrew, and inspect trains. I am grateful for the economic and tactical insights that have been provided. I merely hoped to add some more of the operational aspect to the discussion.
Thank you for your time.