George Westinghouse’s many inventions rank him with Thomas A. Edison and Werner von Siemens as founding fathers of our electrified world. Yet, ironically, Westinghouse’s first invention, a railroad brake he patented in 1869, was actuated not by electrons but by air. To this day, most railroads rely on that system’s principle of releasing air from a pressurized pipe that runs the length of the train and brakes the cars one after the other, at a rate of 152 meters per second.
To compound the irony, some of Westinghouse’s early competitors proposed electrical mechanisms, but Westinghouse himself rejected these as unreliable. In the past decade, however, the idea has reemerged in a hybrid system that uses an electronic system to control a pneumatic one, so as to set the brakes in all the cars simultaneously. So obvious are the advantages of the new technology—called electronically controlled pneumatic braking, or ECP for short—that its manufacturers are optimistic it will eventually sweep the field.
“We believe that the benefits of ECP will be clearly proven,” says Robert Bourg, vice president and general manager of Wabtec Railway Electronics, in Germantown, Md. The parent company, Wabtec Corp., headquartered in Wilmerding, Penn., and the successor to the Westinghouse Air Brake Company, is one of two American companies bringing electronic-pneumatic train brakes to market. The other is New York Air Brake (NYAB), a subsidiary of Germany’s Knorr-Bremse, in Munich.
Two major U.S. railroads have recently begun running , one using Wabtec’s, the other NYAB’s. If ECP brakes catch on here, they’ll likely appear on heavy-haul railroads around the world, especially in regions that adhere to American Association of Railroads (AAR) standards, including southern Africa, Brazil, Australia, even China.
But will ECP, in fact, catch on? Believe it or not, its ultimate victory is not a foregone conclusion. Standing in the way of implementation are steep up-front investment costs and disagreements over who should shoulder them. Such impediments appear whenever an insurgent technology challenges an incumbent—for example, digital projectors in movie theaters and digital TVs in living rooms. And of course, market forces are not the only actors here. Railroads are heavily regulated—and regulation can make all the difference.
The Westinghouse air brake, though updated periodically, retains the basic character it’s had since the 1870s, even as trains have grown much longer and heavier. The locomotive forces air into a pipe that runs the length of the train and connects to a triple valve in each car; that valve connects both to the car’s auxiliary air tank and to its brake cylinder. The relative pressure of the air in the three devices determines the action.
To activate the brake, the engineer drains air from the pipe, causing a disequilibrium of pressure in the valve that moves a piston, which opens a passage from the reservoir tank to the cylinder; this opening, in turn, allows the air to rush in and set the brake. This is a fail-safe design, because if the train were somehow to break in two, the rupture in the pipe would automatically apply the brakes. To release the brake, the engineer sends air down the pipe once again, which fills each car’s reservoir in sequence.
But all this takes time—a 100-car train traveling at 80 kilometers an hour would require at least 1 km to stop. It also takes time to undo the process and get the train moving again.
“We’ve had long trains where the engineer released the brake and started pulling a little bit too early, while the brakes were still set on the rear of the train,” explains Dana Maryott, director of locomotive and air-brake systems at the Burlington Northern Santa Fe (BNSF) Railway. “And coming around a sharp radius, we’ve literally pulled the train off the track.”
Taking a freight train down a long incline is particularly complicated because air brakes cannot be gradually released, the way they are in an automobile, for example. If you try to increase the pressure in the air pipe just a little, the signal will decay after about 600 meters, and it will never reach the brakes in the rear.
To get a feel for the old Westinghouse system, I’ve come to Bluefield, W.Va., at the eastern end of the Norfolk Southern Railway’s Pocahontas Division, 167 km uphill from Roanoke, Va., and another 450 km from the great shipyards of Norfolk and Newport News. Bluefield is America’s oldest “hump yard”; it straddles the crest of a low mountain, so that cars unhitched from the locomotive will roll down to switches where they can be shunted onto the desired tracks.
Today, arriving engineers still drape their trains over the crest so that half the train is parked on each side of the hill. “Once you start heading down,” says Mike Allran, a senior engineering specialist with Norfolk Southern, “gravity’s really going to start pulling on that train good. That’s what makes it tough getting off the mountain out here.”
Sometime after 1 p.m., Train 762—two long black locomotives pulling 110 shiny aluminum cars, each heaped with over 90 000 kilograms of West Virginia coal—arrives at the Bluefield crest. The train, bound for the power plant at Hyco Lake, N.C., stretches nearly 2 km and weighs nearly 18 million kg. I climb aboard Engine 9191, along with Allran, road foreman Chuck Peters, and engineer Jeff Hayslett, while conductor Norris Kasey takes his brake stick and walks alongside the train setting air retainer valves on 10 cars. The valves reserve about 62 kilopascals of air in each brake cylinder, just in case; those cars will be slightly braked all the way to Roanoke. A few minutes later, Hayslett radios his dispatcher and then turns to the rest of us. “Everybody ready to roll?” he asks, and he begins ringing the engine’s bell.
Hayslett eases into his throttle to pull us over the hump, but it isn’t long before he turns to the brakes. The Norfolk Southern, like most U.S. railroads, teaches engineers to control the train as much as possible with the locomotives’ dynamic brakes, which slow the engines by reversing the electric current that powers their traction motors.
In practice, this means Hayslett uses the air brakes to set a base level of braking and the dynamic braking to modulate it. But here the air requires its own precision: If you’re short a couple of pounds per square inch, the train might get away. (One pound per square inch is just under 7 kPa.) But if you’re a couple of pounds over the mark, the train will stall, and you’ll have to fully release the brakes (or “knock off the air”) and then set them up again, probably before the reservoirs are fully charged. In the cab it’s known as “pissing away your air.”
“If you get your train set up the first time right, it means when you go down the mountain you ain’t gotta fight the train,” Hayslett explains. Otherwise “the train’s gonna be working you instead of you working it.”
He applies the dynamic brake, and we can feel a great number of gentle bumps as each hopper rolls into the one that preceded it. A few minutes later, with the train bunched up and the speed approaching 21 km/h, Hayslett grips a lever with two hands and reduces the brake pipe air by 8 pounds. His plan is to knock the air off at milepost N350, a flat spot in the grade where he’ll have time to recharge the system before setting the brakes up again. Next he’ll release the brakes again at Oakvale, W.Va., and then again several miles later, at the start of a very long stretch of flat running.
We breeze through the Virginia countryside. It’s a bright day in May, cool and green in the mountains. At Glen Lyn we meet the New River and follow its winding, tree-shrouded banks, first on one side, then on the other, for the next couple of hours. Then, after a long slog up a 16-km hill, we approach the entrance to the Merrimac Tunnel. Burrowing down for 1.5 km, with a grade of just over 1 percent, the tunnel presents an unusual braking challenge. Without braking, the train will gather momentum quickly. But Hayslett can’t apply the air brakes while he’s in the tunnel.
“Anytime you put the air on, you’re subject for something to go wrong,” explains Peters. Peters is thinking specifically of what’s called a kicker, a sticking valve so sensitive to a reduction in brake-pipe pressure that it begins emergency braking and “kicks” the train swiftly to a halt. Braking miscues like this are called undesired emergencies, and they’ve grown more irksome for railroads in the last 20 years.
Traveling at 32 km/h, our train could stop in as little as 20 seconds if the brakes were applied at full force, Allran supposes. But then the forces acting on the train might be severe enough to cause it to derail. “You don’t want to do that in the tunnel,” Allran says. It’s a matter of fine judgment, notes Peters, who adds that of the 94 engineers he supervises, “there are three or four I wouldn’t want to go down the mountain with.”
Any system dependent on continual human intervention can only be refined so much. By the early 1990s, “the railroad industry recognized that the current air-brake system was an extremely mature technology,” says Fred Carlson, who recently retired as a research engineer for the AAR. “There was very, very little room for improvement.”
In 1991, Dana Maryott and his colleagues at Burlington Northern approached TSM, a small company based in Kansas City, Mo., to develop electronically controlled air brakes. A 65-car coal train, known as a unit train because the cars stay together over many runs, made its debut in October 1993. (New York City’s Metro-North commuter railroad and some other relatively short and interconnected commuter trains, in Europe as well as the United States, have for decades used a fairly rudimentary electropneumatic brake system, but it’s not the one visualized for long freight trains.)
Within two years, the line began experimenting with four more such ECP trains. Each car had a manifold that outwardly resembled the old triple valve, but the system took its cues from a portable computer that stored the car’s unique ID and some performance characteristics, such as its empty and loaded weights. The car control devices, as they came to be called, were in turn controlled by a computer in the locomotive.
In 1995, the AAR, which was separately investigating alternatives to air brakes, convened a committee of railroaders and brake suppliers to write the standards that would govern the new system’s performance and interoperability. They soon faced a fundamental choice: Should the electronic signal to the computer on each car be transmitted by wire or radio?
A wire, like a conventional brake pipe, would need to run uninterrupted the length of the train, meaning that every car would need to be equipped with the new system—a potential logistical quagmire for American railroads, which constantly swap equipment with one another. But a wireless system posed its own problems. Not only would a radio-controlled system require more power (to support the radio in addition to the control circuits), but each car would have to have a power source of its own robust enough to withstand a rugged, moving environment. “We looked at axle generators, air generators, and solar power,” recalls Bryan McLaughlin, who led the ECP team at New York Air Brake, “and none of that technology was reliable and cost-effective enough to put on the cars.”
Moreover, “you need a lot of redundancy and a lot of security for the messaging so that it doesn’t get jammed,” adds the AAR’s Carlson, who coordinated the committee. “Very early on, we had a lot of communications people tell us that if you can do it with a cable, do it with a cable.”
Ultimately, the AAR did do it with a cable, choosing a power-line transceiver by Echelon Corp. , a San Jose, Calif.–based supplier of network control equipment, to thread the signal protocol through the train. The locomotive power supply is 230 volts, based on a 150-car train up to 12 000 feet (3658 meters) long, consuming 10 watts per car.
Additional experiments on other roads followed. But as Carlson’s team finished its first draft in 1997—“probably the best specification the AAR ever wrote,” he says—a funny thing happened: The railroads started to lose interest. At first, “they were pretty much all on board. They wanted a new system, not necessarily interchangeable with the old,” says Carlson. “And then of course, after we developed it, problems began because it wasn’t interchangeable with the old.”
You might think interchangeability wouldn’t be a problem in the United States, where today seven major carriers handle 90 percent of the industry’s business. But there are 560 railway companies in all, operating on short lines and in terminals, and most trains are still strung together and broken apart by turns. In theory, a single incompatible car could thwart an entire train’s braking system, and a single stubborn company could foil implementation across the entire network.
An eye-popping price tag for brake conversion compounds the problem. In a 2006 study commissioned by the Federal Railroad Administration (FRA), Booz Allen Hamilton estimated conversion costs at roughly US $40 000 per locomotive and an average of $4000 per freight car; converting the entire North American 2006 fleet would run to about $7.5 billion. (In 2006, the total capital investment of the seven largest railroads was $8.2 billion.)