Q. What’s a good way to waste millions of dollars of taxpayer money without trying very hard?

A. Wait for a devastating terrorist attack to frighten people, and then deploy at airports and transportation hubs lots of highly visible security measures that make people feel more secure without actually making them safer.

I hate to be cynical, but in the years since 9/11, I have seen this drama play out repeatedly. The terrorists carry out a major attack at home or abroad, politicians call for improved security, and the government engages in a flurry of activity to show it is doing something. After a few months the cost of such measures and their inefficacy becomes clear, and things return to normal.

After the attacks on the World Trade Center and the Pentagon, National Guard troops were deployed to major airports. They lacked the training and equipment necessary for counter-terrorism, but their presence restored confidence in travelers in the immediate aftermath of 9/11. It soon became clear that a sustained deployment was not worth the cost and of no real benefit.

In July 2005, the London bombings revealed the vulnerability of mass transit systems. Once again politicians demanded that the trains be made safer without any real consideration of how or even if that could be done. In response to the outcry, though, the City of Chicago spent more than a million dollars to put additional police and bomb dogs on Loop “L” platforms. City officials might have considered that a smart terrorist would board at 95th Street, Oak Park or Linden with his bomb and ride the train downtown before detonating it.

Beginning in October 2014, the Chicago police began random, voluntary screening of passengers on select CTA trains. Funded by the Department of Homeland Security, the program has been employed on a trial basis over the past year. It looks good but accomplishes little. Any terrorist could easily leave a screening station and board a train at a different place. Unless screening is applied to every passenger at every stop, it will not be effective. Screening everyone would paralyze the transit network.

Given this history of wasteful placebo security, I was disappointed by the local response to the Brussels bombing. Police with assault rifles and dogs now patrol Union Station, and there is more visible security at O’Hare International Airport. Apart from restoring passenger confidence, these measures will not help much. Terrorists are neither stupid nor impatient. They can wait until the furor calms down before conducting another attack or circumvent stepped-up “security.” A would-be bomber could, for example, ride any one of the numerous trains into Union Station rather than come through the heavily-guarded front door.

Avoiding wasteful placebo security does not, however, mean embracing complacency. The TSA, local law enforcement, and Homeland Security work continually to improve transportation security. The best security, though, is invisible. Plain-clothed officers posing as airline passengers would be less obtrusive and, therefore, freer to scrutinize those around them than heavily armed, highly visible security personnel.

An undercover officer milling about the check-in area at the Brussels airport might, for example, have noticed that two of the bombers had gloves on only one hand inside a warm building, a measure used to conceal detonators. Keen powers of observation by trained personnel and an alert citizenry, not more guns, are the key to airport security.

One measure the Transportation Security Administration might consider is to push airport checkpoints outside the terminal doors. Some international airports outside Europe and the United States require passengers to go through security first as they enter the check-in area and again when they proceed to their gates. That measure would, however, create long lines on the sidewalk. These lines could in turn be targeted.

No matter what measures the authorities employ, Americans must face a difficult fact: Complete security is impossible. We can and should work to make mass transit and airports safer, but that should not be done in knee-jerk and wasteful responses to terrorist attacks. We also need to accept that living in an open society with freedom of movement entails unavoidable risk.

Thomas R. Mockaitis is a history professor at DePaul University. He wrote this for the Chicago Tribune. –Ed.

(Tribune Content Agency)