Spanish High-Speed Train Crash Offers Safety-System Lessons

The driver of the high-speed train that derailed July 25 at a sharp curve in Santiago de Compostela, Spain, killing at least 80 passengers and injuring 130 more, told controllers he took the curve at around 190 kilometers per hour, despite an 80 kph speed limit. He survived the crash and is now under investigation by local authorities. Even if the driver turns out to have been responsible for speeding, rail passengers might wonder what else had to fail in the safety system to allow one man’s error to harm so many people.

The crash is the first fatal accident of a high-speed train in Spain, which launched its high-speed network in 1992 and now serves around 100,000 passengers a day. Authorities have not yet assigned it a cause, but it may turn out to be an anomaly. “The most common [reasons for a derailment are] problems with the track or rail and equipment,” says mechanical engineer George Bibel at the University of North Dakota, author of Train Wreck: The Forensic of Rail Disasters. Whereas train accidents from Connecticut to France have made news lately, derailments are a declining threat, at least in the U.S., where they dropped about 90 percent from 1976 to 2011.

The decline has resulted in part from improved monitoring of aging infrastructure such as rails, wheels and bearings, Bibel says. Spanish media reported that the tracks on which this train was running were not designed for the fastest class of high-speed trains. The implication is that the tracks may somehow have contributed to the accident. Lower-grade tracks do vibrate more and wear down faster. And using the same tracks for multiple types of trains, such as high-speed, longer local passenger trains, or even freight, may also promote uneven metal fatigue. Changing temperatures or wet tracks can combine with worn-down train wheels or uneven loading of a train to promote a derailment. Yet things as basic as regular inspections of hot spots with an infrared sensor or of metal fatigue with an ultrasound sensor can alert rail operators to aging infrastructure.

Higher-tech control systems are also emerging. Both the U.S. and Europe are adopting semi-automated braking systems designed to take over from speeding drivers. The track at the accident site, which was very close to the station, used older-generation signaling technology called ASFA, which alerts the driver to upcoming speed restrictions but cannot override his or her control. The Madrid-Barcelona high-speed train line, in contrast, uses the Level 2 European Rail Traffic Management System (ERTMS), which can override the driver. The train drivers union announced that the tragedy “could have been avoided” if ERTMS had been installed on that stretch of track. Even if that is true, Spain already has one of the highest  ERTMS deployments in Europe. In the U.S., rail authorities have warned that they are unlikely to complete a legislated upgrade to similar technology in time for the 2015 deadline.

And Bibel points out that no automatic braking system can cover every scenario: There’s been technology to stop trains since the 1920s but one of the problems is you can’t stop a speeding passenger train the same as a 150-car heavy freight train.” That hasn’t stopped researchers from trying. The U.S. Department of Transportation is conducting work on algorithms that would develop a dynamic custom braking profile for each individual train based on its load (pdf). That might improve automatic control systems, although the performance would still depend on local track conditions, which may be harder to account for.

The high rate of death and injury in the Santiago accident is also anomalous. Derailments tend to be less harmful than collisions, Bibel says, unless they occur on a mountainside, over water or near something into which the derailed train can collide. That is, unfortunately, what happened at the curve in Santiago. The 10-car train skipped the rails, the locomotive began rolling over, and then the train slammed into a concrete retaining wall (video).

Survivors, such as American Stephen Ward, called themselves lucky, and relative to the dead and injured, they are. Yet all the passengers were unlucky in that several systems failed. The train’s still-unexplained speed, the lack of a sufficiently sophisticated braking system, and the derailment next to a concrete wall all contributed to the deaths and injuries.

But not all system failures—or solutions—are technological. “The problem is that you are setting up people to fail,” says railroad systems engineer Felix Schmid, of the University of Birmingham, in the England. “You have a very-high protected railway connected virtually straight into a less-protected railway.” The shift is similar to a car driver exiting smooth traffic on a highway for the less predictable gridlock of a city center.  “It’s the change from low demand to high demand which is sometimes quite difficult to manage,” he adds.

New York City’s Metropolitan Transit Authority learned to cut open-door accidents (in which doors open mistakenly when trains are not safely parked at a platform) by adopting a Japanese human-factor innovation: requiring drivers to signal by hand when they reached the appropriate platform marker for opening the doors. The requirement ensured drivers were paying attention to the shift from low-demand cruising to the more demanding platform stop. Japan also claims to have carried 9.2 billion passengers on its high-speed trains between 1964 and 2009 without a single fatality. That’s a standard to which Spain and all other high-speed rail operators can aspire.

Bibel is optimistic that derailments such as this week’s shouldn’t discourage future high-speed rail projects: “These kinds of accidents have been happening forever. Thankfully they’re rare.”

First published by Scientific American [html] [pdf]

Five Dimensions Store More Data Than Three

An experimental computer memory format uses five dimensions to store data with a density that would allow more than 300 terabytes to be crammed onto a standard optical disc. But unlike an optical disc, which is made of plastic, the experimental media is quartz glass. Researchers have long been trying to use glass as a storage material because it is far more durable than existing plastics.

A team led by optoelectronics researcher Jingyu Zhang at the University of Southampton, in the U.K., has demonstrated that information can be stored in glass by changing its birefringence, a property related to how polarized light moves through the glass (PDF).

In conventional optical media, such as DVDs, you store data by burning tiny pits on one or more layers on the plastic disc, which means you’re using three spatial dimensions to store information. But in Zhang’s experiment, he and colleagues exploit two additional, optical dimensions.

When their data-recording laser marks the glass, it doesn’t just make a pit: it changes two parameters of the birefringence of the glass. The researchers set these parameters, called slow axis orientation and strength of retardance, by controlling the polarization and intensity of their laser beam. Add the two optical dimensions to three spatial coordinates and the result is “5D data storage,” as Zhang calls it.

Previous attempts at storing data in glass consisted of burning tiny holes into the material, but that approach means that an optical microscope is required to read out the data. Zhang’s goal is to write data into glass in a format readable with lasers, like existing optical discs, to keep data-reading costs down.

The writing costs will be higher, though, since changing birefringence in glass requires fine control of a laser’s polarization and intensity. Earlier attempts involved rotating the laser and using an attenuator, Zhang says, but that could take several seconds between writing operations, making it far too slow for practical applications.

Instead Zhang and colleagues bounced the beam of their ultrafast writing laser off a tiny, commercially available LCD-like screen called a spatial light modulator, or SLM (see illustration below). It changes its reflectivity quickly in response to electrical charges, giving the team fine control over the intensity of the reflected beam.

Then, to control the light’s polarization, the team sent the writing beam through a square panel containing 16 subsquares of different colors. Up to this point, the system has no moving parts.

But the quartz glass itself sits on a moving platform. The team achieved writing speeds of around 1 MB/s, Zhang claims. For comparison, that’s about the speed of the first DVDs, and the latest flash memory devices can write a couple orders of magnitude faster.

The laser writes to multiple layers of the glass, making for dense data storage. And previous tests have shown that glass is highly durable and stable up to 1000°C. That makes it a good candidate for archiving applications.

Ultrafast lasers cost more than existing lasers, and glass costs more than the plastic used in DVDs, but Zhang says, “Our main point is that this memory can last very long. If it can last a million years . . . people will like to spend this money.”

In his experiment to demonstrate the 5D method, Zhang stored a text file—the abstract of a talk he gave—onto a 4 centimeter-square blurry piece of glass. The text read:

“The high-density five dimensional data storage with ultrafast laser writing is demonstrated. The text file is recorded by polarization controlled self-assembled form birefringence and retrieved in glass opening the era of unlimited lifetime data storage.”

Embedded in glass, Zhang’s words should last for a very long time—perhaps much longer than in this ephemeral web page.

First published on IEEE Spectrum’s Tech Talk blog: [html] [pdf]

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Argentina cuts GM red tape

homecoverArgentina has streamlined its biotech crop regulatory framework to ensure neither red tape nor international trading partners’ policies hold up commercialization. The country, one of the first to embrace biotech crops, relied for two decades on a hodgepodge of agencies and rules to govern genetically modified (GM) crop commercialization (Nat. Biotechnol. 28, 393–395, 2010). A 2010 reform established a new Ministry for Agriculture, Livestock and Fisheries, which updated and consolidated rules in 2012. This spring, the Ministry packaged those rules in a single booklet for commercial and academic growers. Under the old rules, GM crops that had already passed food safety and environmental impact assessments still needed commercial approval. The commercial committee exercised a so-called mirror policy of approving for cultivation only GM crops that trading partners, such as the European Union, had approved for import. That policy led to one crop being held up for a total of 12 years, says the Ministry’s biotech director, Martín Lema. Now, thanks in part to World Trade Organization rulings and growing trade with partners such as China, Argentina has abandoned the mirror policy. Typical approval times may be around four years now, Lema says, down from an average of five to six years. Other changes include placing time limits on certain stages in the paperwork required for approvals. “While it’s very similar [to the old framework], this one is much more functional…. Industry is in accord with the changes,” says Fabiana Malacarne of the Argentine Seed Association, an industry group in Buenos Aires.

First published in Nature Biotechnology [html] [pdf]

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Spain’s Lead-Lined Lakes

ja13-coverResearchers from the University of Granada collected mountain lake sediments from Laguna de Río Seco in southern Spain that had accumulated over 10,000 years, trapping deposits from the atmosphere. In these stacks of mud, they found fine layers of lead that reveal millennia of metalworking and migration, and may be the oldest evidence of air pollution in southern Europe. “[The mud] has been capturing the evolution of air pollution from the Neolithic to present times and giving us an idea of the activity of each of the populations that have passed through southern Iberia,” says team leader José Antonio Lozano, “such as the Phoenicians, Romans, Visigoths, Moors, and more.”

The team dates the first man-made uptick in pollution to between 3,900 and 3,500 years ago, which matches the appearance at nearby sites of coins, weapons, and decorations that, when made, left behind lead by-products. The lead records also attest to a quiet period, when mining moved elsewhere in Iberia, and to a spike corresponding with a period of Roman mining. But all those signals are dwarfed by a more modern surge, which the team attributes to the leaded gasoline in heavy use from the 1950s to the 1970s. The good news, the researchers report, is that present-day lead levels are already below those of the worst Roman deposits.

This From the Trenches item first appeared in the July/August 2013 issue of Archaeology Magazine: [html] [pdf]

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