Do trains really take a while to stop?

Question

Is it true that because of the massive force and power involved with trains on railroads, they take some time to stop? I heard that because of it’s power once a train gets moving and gains momentum, it takes it a while to stop. For example, someone told me that when they start actually going and they get up there in speed, they have to break like 20 miles before their actual destined stop in order to be able to stop there. I mean it does have a lot of power, which is why it can haul so many carts at one time, so is this correct?

Answer 1

Excellent question, requiring a long answer. I hope I don't put you to sleep.

Getting a train started and up to speed is the easy part. Getting the thing stopped where you want is what train handling is all about, and it isn't easy. There are many factors in determining stopping distance.

One of the things that makes freight trains so economical is they have a low coefficient of friction. Steel wheels on steel rail, and the point of contact is not much more than the area of a dollar. In addition, the tonnage of the train is on roller bearings.

Today's trains, unit trains in particular, such as coal trains, can easily reach 16,000 tons, not counting the weight of the power. If you have five locomotives in the consist, add another thousand tons. To put it into perspective, this tonnage is roughly equal to the weight of 5, WWII era, US Navy destroyers, on roller bearings, occupying little area on the rails and often heading down hill.

The train has but one power source in the locomotive's prime mover, but four brake systems, including engine brake, dynamic brake, automatic brake and hand brake. Let's not detail operation of those systems here, as they should be addressed in other questions about brakes and brake operation.

Now, lets assume we are on a train of loaded cars with reasonable tonnage, 8,000 feet in length, travelling 60 MPH on level terrain. The rate of propagation of air through the brake pipe at a service rate of reduction (not "emergency" or "panic" stop) is, rounded off, 500 feet per second. So, on our 8,000' train when the engineer applies the brakes, they do not apply on the rear car of the train for 16 seconds. So, at 60 MPH you have travelled over 1/4 mile before the train even begins to slow down.

Though signal spacing that creates "blocks" is not a constant, the trackage with higher speeds have signals that are around two miles apart. If a stop is to be made, usually, when passing the last green signal, you will see a "flashing yellow" signal, 2 miles ahead, then a yellow signal, 2 miles ahead, and a red signal, 2 miles ahead. So, in this instance a nice controlled stop takes place covering six miles.

An emergency stop and a panic stop are two different things, but, in an emergency application of the brakes, the air travels at a rate twice that of service, or 1,000 feet per second, and a distance of 1 to 1 1/2 miles to bring the train to a stop is average, on level ground. Factor in grade and the distance increases.

It is important that all realize this. This is why, if I can see you, even travelling at a slower speed of say, ten MPH, I cannot stop for you. The inertia behind that tonnage is incredible.

There are still other factors that determine stopping distance, including Tons Per Operative Brake (TPOB) which is the tonnage divided by number of cars to develop the average per car, wet rail, wind or empty cars, which stop in roughly 1/3 the distance of a load, condition of brake rigging, brake pipe leakage, etc.

A final thought. If the amount of retarding effort by the brake systems could be converted into power, the train would develop enough to put it into orbit.

So, the best thing for some one to do, and what all train crews wish for, is that people stay off the right of way and never cross tracks without looking in both directions each and every time. People who routinely cross tracks on a daily basis can become complacent about the crossings, which means they can become dead. Look, listen and live.

Answer 2

It's a control thing. At that age there is very little they can control in their lives, but they can control their bladders. She is using it to prove she is in control and you are letting her, she knows you will change her when she is wet so why should she try? She also know a fit will work. You need to take back control of the situation. Put the underwear away and make her wear diapers. Tell her she must wear them until she can pee on the potty like a big girl (at least most of the time) because peeing all over the house is not acceptable behavior. I would also try taking away other "big girl" privileges and only letting her have them when she pees on the potty without a fit. If she did it for three weeks then she knows when she has to go, she just sees no benefit in doing it at this point, it is up to you to change that.

Answer 3

The time it takes a train to stop has nothing to do with how much power it has, but how much velocity it has . The momentum a train has accumulated is a product of its mass and velocity. When a locomotive weighing several thousand tons is moving at 60mph just imagine the time it would take to stop in on a track that has little rolling resistance in order to improve travel efficiency. Dividing the momentum by the applied braking force will tell you the time it takes to stop a train.

Answer 4

Well, the time it takes for the train to stop is going to be dependent on the speed it is going. It's basically a physics thing. So the thing you said about momentum is correct. And the longer it goes, the faster it gets, the longer disctance it needs to stop. Also, the tracks are made to have very little friction, which contributes to a longer time to stop.

Answer 5

roughly 2 miles very a real long train

Answer 6

I doubt it takes 20 miles for a "panic stop" at a speed (like 60 m.p.h. But it will take a whole lot further thatn any "big truck" with properly working brakes! Bear in mind that there is very much mass (some times 100 cars or more), and hundreds of thousands of tons of weight. And then there is the fact that lthe "contact area" of the wheels is not very large (compared to a motor vehicle). Nor is the contact area capable of getting enough "friction" (traction) like a rubber tire on anabrasive surface! So you are trying to stop - maybe a mile of heavy stuff by sliding steel on steel. It is definately going to take a quite a while. I have heard that a freight train of moderate size takes almost a mile to stop from about 25 m.p.h. - when it sees a vehicle stalled on the tracks, -- Which means it takes about 3/4 of a mile (maybe) to get to stop-- after it hits it!

Answer 7

trains are not like cars they need alot of time to reduce speed..njtransit conductors need contractnow 2 years no raises..they deserve a raise now

Answer 8

There's no hard and fast speed or weight = stopping distance formula, but I can give you some insight into what factors affect the stopping distance.

Pulling power has almost nothing to do with stopping power. Two 4,000 HP mainline engines will stop almost the same as two 1,800 HP yard engines with an identical train, when the brakes are identically set up.

First of all, weight is an important factor. Locomotives weigh anywhere between 125 to 200+ tons (250,000-400,000 pounds) each. Railcars can weigh 30-150 tons each. Weights vary - I've had a train that was 7200' long and 6,300 tons, another a few days ago that was 4800' and 8,000 tons.

Speed is another. Obviously, a train going 5 mph will stop in a shorter distance than one moving at 50 mph. Again, no hard and fast formula to calculate stopping distance here.

Operative brakes is something else to factor, but often forgotten by non-railroaders. Trains use an air brake system, and the brakes are only operable in as many cars as are hooked up to it. Generally speaking, you'll have 100% operable brakes on a mainline train, but in a yard setting, you could have only locomotive brakes (none of the cars have brakes), or 100% brakes through the cars. Each situation is different.

Environmental conditions also play a part. Rail conditions, such as heat, cold, rain, ice, and snow can affect the braking effort. Grades also play an important role, not to mention curves.

An emergency brake application will stop the train the fastest, however, it's dangerous to do this, as you risk a derailment, load damage, and equipment damage, so it's advisable to not do this unless you absolutely have to.

The 20 miles to stop thing is nonsense - much too far. However, keep in mind that trains will take longer to come to a complete stop, especially an unplanned one, than your regular passenger vehicle.

Answer 9

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