In the rebooted Action Comics issue #1 (The New 52), the police's bullets were failed at shooting the strange new creature which was also known as Superman, so Sam Lane consulted Lex Luthor. Lex Luthor planned to shoot the world's biggest bullet at the face of Superman. He made Lois Lane a bait and caused a bullet train to malfunction.
Well, he was successful. Superman was captured.
Previously in the comic, someone told Clark about the bullet train's problem. He was talking to Jimmy (who was with Lois) on phone and after a scene of Lois & Jimmy, he figured out the bullet train's problem while talking with someone on phone. Then, he texted the problem to Jimmy and became Superman to save train from speeding.
Lex Luthor didn't know that Clark was Superman, so he couldn't do this. Who told Clark about the problem with the bullet train, as it wasn't broadcast to the public?