WHO: An engineer on the Metrolink train that collided with another train in Chatsworth on Friday, killing at least 25 people and injuring at nearly 140.

WHAT: Federal investigators are looking into allegations that the engineer, who apparently missed a signal indicating that another train was coming, may have been text-messaging with someone at the time of the crash.

WHY IT’S HAPPENING: If the claim is true, the incident only drives home the danger of using a cell phone while driving or operating major equipment.

WHY IT’S A BAD IDEA: Rail-safety officials are pushing for a federal law banning the use of cell phones while driving a train. We think this is a matter of common sense.