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Metal detectors at subway stations are probably a bad idea
I just saw a CNN poll which shows that 60-something percent of Americans are in favor of installing metal detectors at subway stations. This is probably a bad idea for at least three reasons:
1. Metal detectors do not pick up explosives and would not prevent bomb attacks such as those that took place in London this morning or in Madrid last year. You need explosives detectors for that. Trained dogs can do a decent job at this, but electronic explosive detectors are currently far too expensive to install most subway entrances.
2. Metal detectors would cause bottlenecks of people lined up to go through them. Such predictable concentrations of crowds in environments poorly designed to accommodate them are attractive terrorist targets in their own right.
3. Setting up visible but mostly ineffectual security devices such as metal detectors may both desensitize and frustrate regular commuters. This could reduce situational awareness and make people less likely to cooperate with other, more meaningful, security measures in the future.
We should remember that
metal detectors were originally installed at airports to prevent hijackings, not
bombings. There is relatively little danger of someone hijacking a
train.
I'm hoping that we'll see a dramatic reduction in both the cost and operating time of electronic explosives detectors over the next few years. That's a technology that could actually make a difference. For now, investment in terrorist response capabilities are just as important as investment in terrorist prevention capabilities. In the case of mass transit, perhaps even more important.
July 8, 2005 | Permalink
Comments
You're right -- metal detectors for subway trains are not a workable idea from two standpoints: travel convenience and efficiency, and security.
The role of airport metal detectors is not to prohibit metal items in general, but to help ensure that no specifically prohibited metal items are carried onto a plane.
The purpose of metal detectors is to ensure that no metal items are uninspected.
Metal detectors are coupled with X-ray machines (for carry-on articles) to ensure that metal as well as other types of items are inspected; only some types of metal items are prohibited. Metal detectors only work as part of an inspection process. Unlike airplane inspection, subway train inspection would have to account for bicycles, shopping bags, guitars, tools and various other items-with-metal that I have seen travelers bring on subways.
Like at airports, this inspection would be a slow and labor-intensive process. Enough physical space would have to exist to be able implement the machinery inspection space and queue lines (which is not the case at any of the subways I have ridden). It would significantly add to train travel time and raise the cost of train travel prohibitively.
Besides, such an inspection process would create new security risks, whose mitigation would raise the cost even more. In his book Beyond Fear, Bruce Schneier spells out a five-step process for evaluating security measures. Step 4 is: What other risks does the security solution cause?
Schneier‘s book was many years away when the FAA implemented the airport security checkpoints. They didn’t realize that because security checkpoints would be (for the first time) separating passengers from their belongings, they would create an entirely new major theft risk. A July 2001 survey of the major airports showed that checkpoint theft (which by that time involved organized international theft rings) amounted to 30% to 40% of the crime that police at major airports had to deal with.
I point this out to show that very careful consideration needs to be given to any major security measure. That's not done often enough.
Posted by: Ray Bernard | Jul 18, 2005 2:06:31 AM
You say there is little chance of someone hijacking a train. Don't be so sure. I can see it now -- Sadam Jr. holding a box cutter to the throat of the subway engineer -- "take me uptown; I go see Central Park or I cut your throat." Or worse, he insists the engineer take him to Los Angeles, so they circle Manhattan for hours until police finally cut the power.
Posted by: Ken Bradmon | Jan 26, 2006 12:27:36 AM
