Something went wrong with the automated control systems on the Washington D.C. mass transit system, resulting in a horrible crash with multiple fatalities.
"That train was never supposed to get closer than 1,200 feet, period," said Jackie Jeter, president of a union that represents Metro workers.
I rode the Metro once, in the early 80's; at that time it was brand new, bright and gleaming.
This investigation is still very early, but it is already known that the train in question was not equipped with any particular event recording information, so there will be less information for the investigators to chew on.
The Metro is similar in a number of ways to San Francisco's BART, which I ride regularly. They are both roughly the same age, use roughly similar technologies, and have broadly similar purpose. There are some quite interesting articles comparing the two systems: here's one from transit planners in Seattle; here's another from a group in Houston.
As transit systems become more complex, the need for automation assists becomes crucial. BART was a major symbol of this in the 1970's: both as a symbol of the importance of automation in modern transit systems; and as a symbol of the complications that come with automation.
California is just beginning work on a massive state-wide high-speed train system, funded by some recent ballot initiatives. The level of automation required for such a system will be substantial; this is of course both an opportunity and a challenge.