From derailments to head-on collisions to drivers killed at road crossings, deadly train accidents claim dozens of lives each year. But just how unsafe are the railroads? NOVA investigates recent rail tragedies and advances in train tech that could help prevent them, taking a special look at Japan's superefficient bullet trains, which have a perfect safety record. What would it take to usher in a new golden age of safer, faster, more modern and reliable train travel?