Two subway trains collided in the city of Shanghai on September 26, injuring hundreds, according to early reports. And, much like the collision of two high-speed trains that killed 40 people near Wenzhou on July 23, the culprit appears to be signal failures.

According to Chinese news magazine Caixin, the signals began to malfunction at least an hour before the crash, which caused operators to attempt to coordinate the system by phone. The signals on the Shanghai system, like the signals on the Wenzhou high-speed rail line and a full 70 percent of the signals on all of China's burgeoning rail network were made by Casco—a joint venture of China Railway Signal and Communication Corp., a quasi-governmental company, and French industrial giant Alstom.

Railroad signaling is an old art given that the "iron horse" has been with us for a couple centuries now. In the old days, railroad operators coordinated trains "by the book," so that trains ran at exactly scheduled times and therefore never collided, barring mishaps.

Of course, that approach worked better in principle than in practice and, with the advent of the telegraph, train operators worked out better and faster ways of coordinating train traffic. Nowadays, block signaling, wherein no two trains are allowed to occupy the same section of track as revealed by color-coded lights and other signals, is coordinated by computers or, in their absence, people.

But the rush to build out China's railway system may have caused some safety lapses. After all, the Shanghai rail system alone now covers more than 450 kilometers, most of that built in the last decade—and signaling problems have been chronic on Shanghai's Metro Line 10 where the collision occurred.

This rush to build is not a problem confined to just railroads. China is currently building more than 4 million kilometers of roads, hundreds of dams and more than 20 nuclear reactors, among other major infrastructure projects—all at an accelerated pace. Perhaps the best way to ensure the safety of infrastructure in China, like the burgeoning high-speed rail network, is to slow down its construction.

Image: © David Biello. I rode one of China's new high speed rail lines myself last fall on a trip from the capital Beijing to Shenyang in Liaoning Province in the northeast. The trains are comfortable, quiet and fast. Let's hope the signal technology can keep up.