If you saw the police and firefighters on the ACE (Altamont Commuter Express) trains Tuesday morning -- don't worry, it's just a training exercise, and it'll be going on all week.
ACE Spokesman Thomas W. Reeves said it's a Transit Safety Administration (TSA) exercise, set to run from 9 a.m. to 3 p.m. through Friday.
"Law enforcement, bomb squads, fire departments from all around the valley will be involved," Reeves said. "They're bringing in K-9 units, basically the whole nine yards."
While the ACE trains are stopped on the tracks, Reeves said they shouldn't be blocking any traffic.
In April, ACE conducted a similar training exercise for 120 firefighters in Santa Clara, teaching them equipment operation and how to access it under emergency conditions.