So what do you do when the system does not detect the failure, as with the WMATA situation? Indeed these situations are thankfully very rare, but possible. We engineers do our best to make sure such events do not happen, but no one is perfect, therefore, mistakes will be made. I think for this reason, it is plausible to expect not only a robust train control system, but a safe mechanical design as well. It creates additional layers of safety, further mitigating any possible accident.

Don't get me wrong - I am all for improved train control. As an engineer, I find such things almost as facinating as the trains themselves. I just don't want us to get lulled into thinking such systems are going to solve world hunger.