How far will a train travel before it can make a controlled stop ?

Question

Will weight and length have any bearing on the safe stopping distance?Speed?Railbed?

Answer 1

All of the answers above have identified some of the many variables associated with train control. Well done. If the "general public" were as aware, then perhaps grade crossing and pedestrian fatalities would be declining instead of rising each year. There are some points to clarify, though, and a couple of variables were not mentioned.

There are basically three methods to halt a moving train. Let's look at them.

The engineer or conductor can initiate an emergency application of the brakes (aka, plug, pull the plug, big hole, wipe the clock, dump the air, and an old term, "gas 'em"). This is the method for the shortest stopping distance. It is also the least desirable, as the potential for a derailment sky-rockets. Though technically not a "controlled" stop, there are measures the engineer can take to mitigate, to some degree, the excessive slack action that is the usual result, primarily by the way in which the engine air brakes, called "independent", "straight air" or "jam", are handled by the engineer. So, it could be said more accurately, that this is a "semi-controlled" stop.

The next quickest way is to put into practice the "surprise stop" or panic stop, as it is sometimes called. This is a misnomer, as almost any engineer would never panic. On the rare occasion when one does, he jumps, usually with the conductor immediately ahead of or behind him. This is a controlled stop, but can also cause damage, and is always avoided, if at all possible.

The conventional, day in day out method is the service stop. The train is in complete control of the engineer.

As already stated, most of the variables relative to stopping distance have been mentioned. But, there is one constant that was overlooked. Time. More accurately, "propagation time". This is the rate at which air is exhausted out of the brake pipe that causes the brakes to apply on each car. Rounded off, at a service rate of reduction the air travels at 500 feet per second. The emrgency rate of reduction is twice that, or 1,000 feet per second.

This is why the length of the train is very important to the equation and should not be downplayed. By way of example, we are on a train that is 8,000 feet long, travelling at 60 MPH. When the engineer makes the initial reduction (sometimes referred to as "first service") in brake pipe pressure, it takes 16 seconds before the brakes on the rear car even begin to apply, which means we have travelled 1/4 mile and are still clipping along at 59 MPH. The initial reduction puts the brake shoes against the wheels and adjusts the slack. Further reductions are made for the braking necessary, but they are still effective only at a rate of 16 seconds a whack.

On most trackage with higher speeds, the signals are around two miles apart, but not always. This is probably a good average and what we will use for our purposes. After passing the last green proceed signal, the next signal will display a "flashing yellow" aspect, followed by a "yellow" aspect and finally the red signal. The engineer has six miles to make a controlled stop. On tracks with even higher speeds, there may be an initial signal aspect of "flashing green", where the allowance is eight miles.

A variable that was overlooked is Tons Per Operative Brake, or TPOB. This is a figure that is arrived at by dividing the total trailing tonnage by the number of cars in the train to arrive at an "average" for each brake in the train. Though length is still a factor for the reasons above, a short train can have very high TPOB and its stopping distance may be more than that of a longer train with lower TPOB.

This is especially true when operating as a "lite engine", which is one with no cars. Five units will weigh in at over 1,000 tons and still requires a long distance to stop. This is what gets some people clobbered at grade crossings, as they assume an engine can stop very quickly with the absense of the cars behind. This is not true. In additon, familiarity breeds contempt. Sometimes people who regularly cross the tracks at the same spot several times a day as a part of daily routine get used to the plodding nature of the beasts usually seen there, and will try to beat a lite engine that is travelling much faster. Wham! Someone is going to collect your life insurance. Look and listen each and every time you cross tracks anywhere. Your life and the lives of loved ones depend on it.

Other variables would include wet rail, whether the locomotives were working power or dynamic brake or whether the brakes were already set for speed control when the stop was initiated, sight line, brake pipe leakage, whether the air brake system was fully charged and the overall condition of brake shoes and rigging.

The bottom line is, whatever method is employed, a great distance and significant amount of time is needed to bring any train to a stop. If you want to make it home for dinner tonight, stay out of the way today.

An informative question. Thanks for asking.

Addendum: If anyone thinks I bang the safety drum too loud or too much, pay close attention to the answer from Wittster below!

Answer 2

By controlled stop, i would assume that you are referring to the train not having to make an emergency application of the brakes (otherwise called "plugged" or "big holed") It depends on how long the train is, what is the total tonnage... if the majority of the train is heading uphill, or downhill, how fast is the train moving, what is it hauling (liquids slosh in the tanks, making stopping more difficult)

Weight has more bearing on safe stopping than length has.... for example, you could have a 6500 ton (assuming 50 cars weighing 30 tons a piece with 100 tons of material) train that is only 50 cars long (approx 2500') all cars being loads, which would take more braking effort to stop the same length of train all cars being empties (approx 1500 tons)

The empty train could stop in about 1/4 of the distance that the loaded train could because of the tonnage alone.

Newer cars with the newer brake equipment seem to stop alot easier than the older cars with the worn brake equipment.

Engineer makes a big difference as well depending on whether or not, he knows the territoty that he is traveling very well, and where his train is at (loads coming down over a hill running in, and pushing the train instead of being drug by the engine)

I hope that this is enough information for you.

Answer 3

Just yesterday I plugged (full emergency brakes) the train at 70 mph. We came around a curve and saw that this guy was laying down between the tracks. So, it was about a 1000 feet to him and by the time we fully stopped it was about 3000 feet past him, for a grand total of about 4000 feet! Our train was 6700 feet (all loads, no empties)and I had to walk back to see if we hit him or not? We did, he was still alive for about 30 min. So, there are so many variables in stopping a train to tell you the exact footage. I can tell you that every 18 sec. there is a accident somewhere in the US. The best thing about hitting someone, is that I get 3 days off with pay! This is number 9 for this year! Do I feel bad? Kinda, but not really. After all they all are trespassing on private property....

Answer 4

There are several fctors regarding the stopping distance of a train
Speed
Grade
Train engine size
condition of train brakes
combined weight being hauled

Answer 5

The only significant variable is speed. The length of the train does not matter as all the cars have brakes. The roadbed does not matter at all. The weight does not matter because a heavier train has higher friction.

Answer 6

Most trains will be fully stopped in 30-40 seconds. Definately not fast enough to stop if an unexpected object is put in it's path.

Answer 7

Speed, weight and incline will all have a bearing on stopping.

Answer 8

All depends upon the weight, usually a half mile

Answer 9

about 1425 ft 6 inchs if did,nt hit a large truck.. it would be less 6 inchs lol