Potential Causes of DC Metro Crash Arising-Signals and Operator Combined?

Metro was designed with a fail-safe computerized signal system that is supposed to prevent trains from colliding. The agency's trains are run by onboard computers that control speed and braking.

 Another electronic system detects the position of trains to maintain a safe distance between them. If they get too close, the computers automatically apply the brakes, stopping the trains.

 These systems were supposed to make yesterday's crash impossible.

 But four years ago, in an episode eerily similar to yesterday's, the signal system briefly failed in the tunnel between Foggy Bottom and Rosslyn, forcing two quick-thinking operators to stop their trains manually to avoid a crash.

In the June 2005 incident, the operator of one train noticed that he was getting too close to the train ahead. The signal system was telling him the track was clear, but he hit the brake. The operator of a third train on the line hit the emergency brake on time, too.

In yesterday's crash, it appeared the operator of the train that crashed did not apply the emergency brake, also known as the "mushroom."

There was no reason to think the operator did not spot the train ahead of her yesterday. The weather was clear, and the trains were not in a tunnel.

With a staggering number of injured passengers, its a certainty that they will want to know who is responsible for causing their horrible injuries, and many will have permanent effects.  This type of crash requires not only a mechanical failure, but combined failure of an operator to keep a proper lookout.  Its a wreck that should have been prevented by electronic controls, as well as human factors/proper lookout.
Our hearts go out to the victims and their families.

Either the NTSB or Federal Railroad Administration will have preliminary reports in the near future.

For prior articles on this and related topics:
Metro Railroad Trains Collide Outside Washington, D.C.--At Least Six Dead, 60 Injured
At least 6 Dead, 60 or More Injured in Washington, DC Area Metro Train Crash
Metro Trains Collide Outside of Washington, D.C. During Rush Hour Traffic
Washington, DC Train/Rail Disaster Kills At Least Seven & Injures More. What Does It Mean For Austin?
Washington, D.C. Nightmare As Metro Trains Collide-- As Many As 7 Dead and Over 70 Injured
Death on Rails