As part of its heightened security, Amtrak is requiring passengers to show photo identification when buying tickets, checking baggage or sending packages by train.

The rule, announced Tuesday, will not apply to riders who buy tickets at unmanned, automated terminals. But Amtrak says credit card information from those outlets "may be used for internal security purposes" as well.

Amtrak, the nation's passenger railroad, has been bolstering its security since the Sept. 11 terrorist hijackings of four airplanes and attacks with three of them on the World Trade Center and the Pentagon. Other steps include inspections and sweeps of stations, property and trains and an increased presence of uniformed officers on trains and in stations.

Amtrak has a nationally accredited, 325-officer police force. Amtrak Police Chief Ernest Frazier said the railroad may take other steps "to maintain a secure environment on board our trains and in our stations."

Currently, passengers and their bags are not searched or screened before boarding Amtrak trains. Amtrak says people will now face questions about bags being checked or packages being sent, similar to questions commonly asked at airport counters.

Amtrak accepts packages through its mail and express service.

Amtrak asked Congress last week for $3.2 billion to increase service and to enhance security by, among other steps, hiring more police officers and installing new security fences and video cameras on rail property.

Demand for Amtrak seats spiked last week when airlines were temporarily grounded. Amtrak registered a 17 percent gain in ridership during the six days after the Sept. 11 attacks.

Amtrak officials say their trains continue to carry 10 to 15 percent more riders than they typically did before the Sept. 11 attacks.