Two years ago, after bombings in London's transit system, the New York City Police Department began randomly inspecting the backpacks and packages of subway riders. The program remains in operation, says the New York Times, at exactly the same level as when it was introduced. Officers set up inspection posts at least 35 times a year in each of the city's 468 subway stations. The operations go on 24 hours a day, sometimes in the middle of the night, and for several hours at a time. More than 300 posts are set up each week, for a total of more than 30,000 checkpoints since the program began.
The police department has contributed to the almost phantom nature of the program by refusing to divulge precisely where the units are set up or how many officers are involved – even successfully defeating a lawsuit seeking just those facts. Terrorism experts said the program's effectiveness was not so much that it is a tight barrier to keep terrorists out of the subways, but that its fluid nature could keep any attack planners off balance. “When you have randomness, it is more effective than when you do it all the time,” said Timothy Connors, director of the Center for Policing Terrorism at the Manhattan Institute for Policy Research. “If you have a predictable regimen, it can be exploited. That's what the 9/11 hijackers did.”