Amtrak has begun random checks of passengers' IDs as a precaution against terrorist attacks.

The onboard checks, which started at the beginning of this month, are part of a broader program to improve security, according to Amtrak officials.

Amtrak also is requiring passengers to show identification when buying a ticket at ticket counters and to tag all luggage with the owner's address.

The new measures have not resulted in any arrests yet.