A vigilant nation, or tattletale America?

Diesel rigs rumble through the Triple T Truck Stop, where Gerald Crews and Walter Getchell are climbing down from their cab en route to California. Since Sept. 11, more than just the endless highway has made a break welcome.

"We're nothing but nervous out on the road these days," Mr. Crews says, rubbing a stubbled chin. "We're always keeping an eye out for suspicious-looking loads, drivers who are acting erratic."

Like millions of Americans, these truckers consider themselves the eyes and ears of homeland security. They're on the lookout to spot anything amiss on America's interstates, whether among the drivers or cargoes. If something does turn up, they wouldn't hesitate to call it in to state troopers - hardly the people they normally want attention from.

This kind of citizen vigilance has resulted in nearly a half-million calls to the FBI, and thousands more to local law-enforcement agencies. A few of those tips have proven valuable: Clayton Lee Waagner, suspected of mailing hundreds of anthrax threats to abortion clinics, was arrested in December after being spotted by a Kinko's employee. And an English professor in California alerted authorities when a student, who was later found to have terrorist ties, wrote two of the hijackers' names on an exam booklet.

But by and large, the barrage of calls from a worried public has borne few results, other than a costlier and heavier workload for law-enforcement officials. Critics worry that this campaign - a so-called "national neighborhood watch" encouraged by government leaders, but with few guidelines - threatens to make America a country of tattletales, a place where innocent residents need to be on guard against false allegations.

"The general idea that people should be watchful is not objectionable," says Elliot Mincberg, legal director of People for the American Way in Washington. "The problem is, will it go too far? Will it produce an hysteria, or overconcern?"

The results of misplaced suspicion have been seen across the country:

• In Amherst, N.Y., police responded to repairmen who thought they'd seen a photo of Osama bin Laden in an apartment, and a postman who said he'd delivered a letter with Arabic writing. But officers soon learned that the individual was an innocent engineering student.

• Atlanta police heard that a young man was taking photos of a downtown federal building, only to find that he was researching an architecture class project.

• In Los Angeles, officers constantly receive reports about bags left unattended around City Hall - which inevitably belong to homeless people.

So far, the brunt of these suspicions has been felt primarily by people of Middle Eastern origin. While more than 1,100 people - nearly all Middle Eastern - have been held by authorities, most are found to have no terrorist links.

Since Sept. 11, the Washington-based American-Arab Anti-Discrimination Committee has responded to more 500 incidents of violence and 400 reports of workplace discrimination. "We're especially seeing this overzealousness in situations where people are denied public participation, such as on passenger flights, where this attitude has been directed toward people of perceived ethnicity," says committee spokesman Hussein Ibish.

Law-enforcement agencies can also face the downside of public overreaction. Authorities estimate that 99 times out of 100, a call is over nothing. "Police chiefs are talking about the amount of money they spend on bogus calls," says Arnold Ajello of the Community Policing Consortium in Washington. "And they're finding that there's no terrorism out there."

To cut down on calls, police are trying to educate the public about what constitutes a real threat. They are encouraging people to think more like police. "They're saying, 'Listen, we appreciate the fact that you've got to be more careful, but just because someone appears to be Arab, don't jump the gun,' " says Mr. Ajello.

The FBI, meanwhile, is urging people to share their concerns with friends or neighbors first. "What's suspicious to one person may not be suspicious to another," says Ed Hall of the FBI's Phoenix office.

Suspicious substances have prompted one of the biggest flurries of calls to police. After the first anthrax scare, for example, the Pima County Sheriff's Department, which includes Tucson, "was handling 30-plus calls a day," says Capt. Frank Duarte. "But it's leveled off. Now we get maybe 30 a week."

Sgt. Judy Altieri of the Tucson Police Department adds that the slowdown has been especially welcome following the crisis at a local television station in early October. A producer there opened a letter laced with white powder, which later proved harmless. "After that, we had to come with up with a system for handling those calls, because we couldn't respond to every one we received in that manner," says Sergeant Altieri.

Still, authorities agree that an alert public is crucial for thwarting terrorist activity. "We're aware that people in their own neighborhoods are best able to know if something is suspicious or not," says Mr. Hall.

Big retailers are also trying to be on the lookout, while not frightening away customers. Of course, if something does appear suspicious, handling it can be a delicate balancing act. "Here's the law, here's what they can and cannot ask, here's what action they can take if a person looks suspicious," says Nancy Smith of the Association for Independent Growth in Philadelphia, which provides employee-management advice.

At the Triple T Truck Stop, Mr. Getchell says he's not about to let down his guard. "You never know what's going to happen from one moment to the next," he says, leaning against his truck that's adorned with several flag decals.