Astro Boy: Tetsuwan Atom - episode 8 - 24 May, 2003

Dr. Katō plants a bomb on the Neon Lights, the first ever fully robotic train. He says that the bomb will explode when the train's speed drops below 70 kilometers per hour with a large number of passengers on board. There is an energy plant, Geoworm, in the train's path, and if it doesn't stop, a catastrophe will occur. Atom, who is on board, desperately searches for the bomb to save the people, but even with the latest-model scans, he cannot find it. (Source: Wikipedia)