Episode 8 in the 2003 series.
This episode shares similarities to the 1980 episode The Runaway Subway Train
Kato attacks the Ministry of Science, throwing Dr. O'Shay and the police off guard. A holograph declares that something bad would happen in three weeks.
Three weeks later, Dr. O'Shay attends the opening of a new robot train, the Neon Express. Shortly into the journey Astro declares that he has heard a bomb. After Neon Express scans the train, the bomb is located in the dining room. However, it is only a holographic projector, and it tells O'Shay that a hyperacceration device is hidden in a place scanners would never scan.
After Astro manages to keep the train from derailing, he gets to passengers safely over to another train, and then proceeds to search for the virus. Then something hits him: a scanner can't scan itself. Fortunately Astro defuses the virus and all is saved.