Once again, everyone with an internet connection has become an expert at train braking systems and why or why not they would/could/might have helped avoid the latest derailment disaster.
I'm here to help! First of all, I know a good bit about he basics of train braking, and a good bit of history, but I'm not an expert, by any means. Every railroad has an expert or two whose only job is brake equipment. I was not one of those guys - God bless'em. But, I did rub shoulders with them from time to time...
So, lets start out with some history and basics.
Once upon a time, a train was a locomotive and a few cars. The steam cylinders and drive rods made it go. A lever with a shoe that pressed against the driving wheels provide braking. The might be able to slow down a bit faster than it accelerated, but not much.
Trains got longer and had couplers so you could add and subtract them from the train. Locomotive brakes weren't enough, so they added brakes to each car. A man would walk along the top of the train and apply the brakes on the cars, as needed.
Clearly, this wasn't a great way to control trains, particularly as trains got longer and heavier. The brakemen would fall off trains, get clobbered by bridges and tunnel and trains would occasionally run away down hills if braking was insufficient for the grade.
A solution for better train braking was needed. Many patents were filed. Enter Mr. Westinghouse. He invented the train braking scheme that is in use to this day.
It did two things. Provided power for braking. Provided centralized control of braking. The genius of it was it:
1. did it with a single air line running the length of the train providing both the power and control in one
2. stored the energy to power the brakes on each car
3. was fail safe as the brakes applied if the air line was broken
4. did it simply with a single air valve, an air reservoir and a brake cylinder on each car.
Simply, you pumped up the whole train, filling the reservoirs in each car. When you wanted to apply the brakes, you let a little air out of the air line (called a brake pipe or trainline). This caused the valve on the car to send some air from the reservoir to the brake cylinder. The more you let out of the brake pipe. the more braking you got.
When you wanted to release the brakes, you pumped the brake pipe up and the brakes released.
The control was a valve in the locomotive. The locomotive had to have a compressor and an air reservoir to feed the brake pipe.
You can see that if the train were to break in two, all the pressure in the brake pipe would be gone and the whole train would have maximum braking applied. The inter-car connectors for the air hoses between cars, a.k.a "glad hands", were designed to slide apart if the cars were uncoupled and separated.
Great! Problem solved! We're done...
Not so fast.
There were all sorts of improvements made over the years to make the air brake system work more reliably, improve safety, and allow longer, heavier trains as technology and material improved. Still, the system leaves a lot to be desired.
The two big drawbacks of the air brake system are the co-mingling of the power and control signal. Trying to send a pressure wave signal down a long, winding pipe of pressurized air that already has some flow in it due to many small leaks, is difficult. The pressure wave signal has to be be big enough to be seen by every car in the train but not too big to tip every car into emergency braking (improved emergency braking is one of the big improvements made over the years). You can only let air into or out of the trainline at a controlled rate, through the valve on the locomotive.
The other is the speed of sound. The fastest you can get a pressure wave to propagate is the speed of sound - about 1000 feet per second. So, on a 10,000 foot train, that's 10 seconds front to rear. Add in the damping in the brake valves and friction in the braking rods and levers and it takes even more time to develop full braking pressure of the brake shoes against the wheels.
Freight car couplers are attached to the car's frame by a spring (usually made of rubber pads) in order to allow them to couple to each other without damaging the car. The distance the coupler can travel forward and back on the car is called "slack". When you start pulling a train and stretch it, the slack "runs out", when the train is pushing on the locomotives, the slack "runs in". Controlling the slack when running a train is one of the hardest parts of an engineer's job, particularly where the terrain is undulating. When the brake are applied, they actuate from front to rear and the slack will tend to run in. If it runs in too hard and fast, it can actually cause a derailment in certain cases.
On top of this, add that rarely does a the car's braking system know if the car is loaded or empty, so it is calibrated to assume the car is empty so the wheels don't slide when the brakes are applied. It takes a long time and a long distance to stop a freight train.
Yet, despite these flaws, the system has worked well and reliably.
But, in the past several decades, technology has pushed ahead and an opportunity to improve train braking appeared to be possible. If you sent the signal to the brake valve electronically with a speed of light signal - 186,000 miles per second instead of as a pressure wave in the trainline, you could get all the brakes to apply at the same time, right away. This would make trains stop faster and with greater easy.
All you have to do is put a microprocessor and an electrically activated valve on each car.
Simple, right?
No. Remember, there is:
1. no power on the freight cars to operate the microprocessor and the valve.
2. no wire running through the train to send the signal.
Where is there power? On the locomotive. So, the best solution seemed to be run power and signal from the locomotive to each car. In order to get enough power to every car, it turns out the voltage needs to be over 200 volts. That's a lot. And, the control signal has to run down this same wire. And, I need a connector between each car that can pull apart without damage and make and maintain a solid connection in the rail, snow and dirt of a railroad environment. Not an easy task.
But, every journey starts with the first step. In the early 1990s, the supply industry started developing some hardware and the railroads started running one or two test trains with the new ECP braking systems. Because the equipment isn't compatible with regular airbrakes, entire trains and their locomotives had to be retrofitted for the test. Railroad run some trains of single commodity, like coal, that run back and forth between shipper and consignee without uncoupling and cars. These are called unit trains and this is where the ECP braking systems were tested.
The good news, is they worked - superbly. Braking distances were cut roughly in half. Train crews talked about the responsiveness as being "sports car like". This virtually eliminated the risk of derailments from slack running in and out.
The bad news was, lots of teething problems. Most notably the connectors. Carrying 200 volts down the length of the train with enough current to operated the valves caused a lot of burnt connectors. This was especially disconcerting because the connectors weren't being plugged and unplugged. They were being left alone, for the most part.
So, the supply industry started to improve the hardware and the railroads increased the number of test trains from one or two to a small handful. The improved hardware made regular service on unit trains look feasible.
Here's a look at the state of the art equipment:
https://www.wabteccorp.com/digital-intelligence/electronics-and-components/ecp-4200
So, what happened? Why don't we have this stuff on every unit train now? A few reasons:
1. Current air brakes are cheap, supremely reliable hardware and flexible - same for all railcars and locomotives. Running some trains with and some without is difficult from locomotive fleet perspective.
2. ECP braking is somewhat costly to disruptive to apply. Cars have to be out of service. People have to be trained to operate and maintain.
3. Many trains, particularly unit trains, are run with privately owned cars. Getting them to accept any additional cost is problematic. It was like pulling teeth to get them to agree for $40 a car for automatic equipment ID tags.
4. About the same time ECP was gaining momentum, the industry was disrupted. A model where railroad operations are leaned out, eliminating any resources not needed to just run the optimized operating plan, too hold and spread to all railroads. This model is called Precision Scheduled Railroading or, PSR, and needs it's own blog post to explain. However, PSR made it extraordinarily difficult to spend time, human and material resources on advancements.
Meanwhile on the oil patch... Fracking started making crude oil available in new places. The only practical way to move it was by rail. A lot of this oil was not de-gassed, meaning the tank cars hauling it were very flammable. A few spectacular derailments and fires got the FRA's (Federal Railroad Administration - US DOT) attention.
They, and the NSTB were frustrated at the lack of development of ECP braking and saw that some of the derailments would have been less severe if the trains had ECP braking. So, a regulation to equip these trains with ECP was put forward. The railroads fought it for the reasons listed above. Money, time, effort, minimal or no hard economic benefit. And they eventually prevailed and got the regulation withdrawn.
In my opinion, the railroad's fight against the regulation is both justified and unjustified. It is justified because the "power from the head end" style of ECP braking is a terrible idea. Higher voltages are dangerous and the connectors maybe okay for unit trains, but will be a horrid mess once you try to apply this to cars that are coupled and uncoupled a couple times a day. Technology now includes several ways to power a freight car that didn't exist when this path was chosen in the late 1980s. There are solar panels, generators that can be incorporated in axle bearings, and small air turbine generators now that didn't exist then.
In fact, there are specialized trains that have solar panels, microprocessors and automated unloading gates on them for dumping ballast on the tracks. The end of train devises that monitor the air brake pressure, display a flashing light and have a valve for actuating the brakes, have a small air turbine to charge the battery.
I think each freight car should have it's own power supply and storage battery to power the ECP braking system. This is an area where there needs to be some development effort before a solid standard can emerge, however.
The data trainline to send a signal to the brakes becomes simpler once the power supply requirement is removed. In fact, it might not have to be a wire at all. Why not something like directional Bluetooth? The trick is that each car can only "talk" to it's neighbor, not the car on the adjacent track or two cars ahead. Another thing that would require some development.
But, it would all be worth it. Once you have freight car with a brain and power supply on it, you can do all sorts of beneficial things.
You can monitor the car's health. Some possibilities, on board bearing temperature and detection. Car suspension issues - rocking, bouncing, hunting. Wheel defects - hollow tread, thin flange, out of round. Fatigue life management of coupler and draft gear. This should reduce the incidence of mainline derailment due to equipment condition many-fold.
Also some operational and commercial stuff.
Lading condition - temperature, pressure, leaks, forces on lading with real-time feed to customers. Greatly reduced time for trains to add and drop cars - "pumping up" the trainline is through a wide open feed at full main reservoir pressure instead of through a choked feed valve.
Best of all, you can monitor and manage braking force by reacting to incipient wheel slide. This can greatly reduce braking distances. Stopping in 2000 feet from 60 mph should be doable.
So why isn't this happening?
The biggest one is no one has been able to provide leadership that leads down the implementation path. Managing through the change from standard to ECP braking is fraught with problems. Should cars have both systems for a while? That's expensive and hard to manage. You'd need a valve to cut one system in and the other out . Where is the interface? Every car would have to have ECP before you could run and ECP train. Do you leave a few unequipped cars behind or what? Every railroad has to take the same path at once - in all of North America - like gauge and couplers and airbrakes(!) in the 19th century. And what of those pesky private cars owners? They are about 1/3 of all the cars in service.
The usual path for improvements is that they have to provide hard savings. Many of these things have hard costs and soft savings. Railroads have, by their own choices, decided not to invest in technology with soft savings. Large organizations tend to think this way. They often need to be pushed.
Conclusions:
1. Railroads made a big mistake failing to continue to push ECP braking, being more interested in PSR and mergers and takeovers. Being distracted by Wall Street is no excuse. You need good leaders to sell what's important to the Street, not the other way around. After all, CEOs get paid a boat load just for this.
2. The current state of the art is already outdated. Might as well start fresh and try to develop a more up to date and robust system.
3. The railroads have the money, but they might need to assemble a sizable team, with good participation from the trade organization (AAR) and goverment (FRA).
4. The time to get busy is now.
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