ATLANTA (AP) -- As Todd Henry wheeled his rolling suitcase along the southbound platform of MARTA's Five Points train station, he passed a pair of police officers dressed in olive coveralls and carrying M-16 rifles. A black bomb-sniffing dog was at their feet.
''It's starting to look like South America,'' said the 41-year-old Georgia State University astronomy professor who was taking the train to Hartsfield-Jackson Atlanta International Airport to catch a flight to New York. ''I guess this would be a prime spot (for an attack) ... But you can't protect everything.''
In the wake of Thursday's London terrorist bombings, Atlanta's MARTA train commuters were greeted by heavily-armed police and bomb-sniffing dogs. Public transportation authorities in Atlanta dramatically increased security as the nation's terror alert level was raised.
Homeland Security Secretary Michael Chertoff said Thursday the heightened alert applies to regional and inter-city passenger rail, subways and metropolitan bus systems. Chertoff said that U.S. authorities have ''no specific credible evidence'' pointing toward a similar attack in the United States. He said those who use mass transit should continue to do so.
The bombings in London didn't affect Atlanta communters. The number of riders on the city's mass transit system was average for a weekday, officials said.
At least seven officers armed with M-16s were posted at a main MARTA station in the heart of downtown Atlanta, just five blocks from the site of the 1996 Olympic park bombing. Other officers combed the transit line's platforms and tracks. More frequent than usual, loudspeaker announcements were urging passengers to report suspicious bags.
Joselyn Baker, spokeswoman for MARTA, said all of the Atlanta rail transit system's police officers, including dogs, were deployed. In addition, the transportation agency has asked other police agencies to send officers to help increase visibility.
''There are a number of plans that are constructed for situations like these and those plans have been put into place,'' Baker said.
Despite the bombings and the increased terror level for the nation's mass transit systems, many MARTA riders said they were not concerned about being the target of a terrorist attack. However, they also added that they didn't think extra police and dogs would deter a terrorist attack.
''I don't know any reason for terrorists to attack here,'' said Wendell Hamilton, a 71-year-old retired physical education teacher.
In contrast to the MARTA line, security at the Atlanta airport appeared light Thursday, with only a police officer roaming the airport's main atrium on a mountain bike and a pair of bomb squad officers enjoying lunch in the nearby food court.
''The (security) line I saw was pretty long, so I'm hoping they're inspecting things pretty well,'' said Sarah Roberts, 26, of Stratham, Ga., who was on her way to Tampa, Fla., for a vacation.
Homeland Security spokeswoman Katy Montgomery said with better baggage screening, armed pilots and air marshals and other improvements, including reinforced cockpit doors, ''the U.S. aviation system does have a significant level of security in place already.''
''We encourage the public ... to be aware of their surroundings and report any suspicious activity they may notice to local law enforcement members,'' Montgomery said.