The fumblewear bomber may have experienced one of the classic fails in terrorist society, but he’s clearly having an impact nonetheless. Senate Minority Leader Chuck Schumer (D-NY) is pushing a sense of urgency in getting some sort of bomb detection system in place in the nation’s mass transit hubs such as bus and rail stations. This is an understandable, if reflexive response to an attempted terror attack and if it could be implemented both safely and effectively I’m guessing most of us would be willing to at least give it a look. But can it be done? (Associated Press)

Screening devices that detect suicide vests like the one that exploded in a New York City subway tunnel are being tested in a Los Angeles transit station, but U.S. Sen. Chuck Schumer said Sunday the Transportation Security Administration should speed up plans to deploy the technology nationally.

“The fact that we have this new, potentially life-saving technology at our fingertips — an ability to detect concealed explosives worn by cowards looking to do us harm — demands the federal government put both the testing and the perfecting of this technology on the fast-track,” Schumer said. “We not only want these devices in America’s busiest cities, like New York, but we need them here.”

The Los Angeles Metropolitan Transportation Authority is partnering with TSA to test devices known as stand-off explosive detection units, which do a full-body screening of passengers walking through a station without slowing them down. If an explosive device is detected, it triggers an alarm. The operator, a transit employee, sees a camera image of the passenger on a computer screen, but no anatomical details.

Attacks by Islamic extremists are a fact of life now, unfortunately, so I don’t want to just write this idea off without giving it a fair shake. But there are some obvious questions to be answered right up front. The standing issue with adding more layers of security at travel hubs is that no matter where you put the security wall, people will begin backing up there. All such a plan does is move the soft target further away from the central location, providing a potential bomber with even easier access to a crowd. The description of the new screening system being tested claims that it conducts, “screening of passengers walking through a station without slowing them down.”

That sounds great, but is it even possible? The feds are currently testing QinetiQ’s SPO stand-off threat detection system. I’ll confess that I was not at all familiar with this technology so I had to do a bit of digging. Rather than some sort of x-ray or body scanning machine like we go through at airports, this is a passive system which detects millimeter band light and heat emissions (I think?) from people passing in front of the sensor looking for anomalous regions where the person might be hiding an explosive belt or other device. This brief promotional video from the manufacturer gives a rundown of how it’s supposed to work so take a look.

If you watch the video you’ll see that it really looks like the system still needs each person passing through the security area to come up one at a time and be scanned by the camera. Yes, that’s probably at least somewhat faster than emptying all your pockets, going into the airport’s full-body scanner and holding up your arms while it spins around, but it still requires people to stand in line and approach the scanning area one at a time. Given the crowds of people who walk en masse through the Port Authority in New York City at rush hour, this would still create a massive logjam of humanity, perfect for an aspiring bomber.

We also need to consider the dual questions of false positives and what happens if you actually find someone with a suicide belt on. This is really bleeding edge technology so I was unable to find any data on testing and false positive rates, but if the system is triggered, won’t you need to shut down the entire flow of people entering while you check it out? It would only take one or two in an hour to have the entire platform access area grind to a halt in a busy rail station.

And what if you do find somebody with a suicide belt? The video shows actors who are “detected” with a bunch of fake C4 strapped around their waists looking glum and guilty after they are “discovered,” but an actual bomber’s first reaction at being pulled out of the line for a physical inspection would be to just detonate the bomb, right?

I’m all for investigating any viable options to increase security, but if we’re going to do this at the bus and rail systems they will become even more of a nightmare than the airport TSA stations already are. (The number of people using the subway system in New York City each day dwarfs the traffic at a major airport by several orders of magnitude.) At that point, we may as well just shut down mass transit entirely. If somebody can make Schumer’s idea actually work I’d be all for it, but this looks like it cause more problems than it solves.