WASHINGTON (AP) — Metro officials say a hardware failure caused their train monitoring system to shut down twice over the weekend.

All trains on the Washington-area transit network were halted for about a half hour each time the system failed.

Metro says a computer module about the size of a pizza box failed, impacting the data used to monitor train movement through the system. Technicians replaced the faulty module early Wednesday before the start of train service.

Metro is investigating what caused the module to fail.

The glitch did not affect Metro’s signaling system, which ensures that trains maintain enough space between them. But it
affected Metro’s ability to see where trains were on the lines.

(Copyright 2012 by The Associated Press.  All Rights Reserved.)