Over at Educated Guesswork, EKR has a nice analysis of the potential effectiveness of random bad searches on the subway

If searches are conducted randomly, then on average each additional officer devoted to searching will increase the chance of detecting a terrorist by 480/5 million, or about 10-4.

…

Of course, this depends on some pretty charitable assumptions, namely:

1. The rate of attempted attacks will be substantially higher
2. People don’t blow themselves up when detected.
3. That people who are detected don’t just come back later try again.
4. That you can do a reasonable search in a minute. The TSA secondary screenings I’ve been on seem to take more like five.
5. That the terrorists won’t shift to some new target. Railway stations are good, but so are airports (outside the security perimeter), shopping malls, etc.

I’m not sure I believe any of these.

Me either.

More likely the attackers will deliberately target the queued up lines of people, which would seem a logical response and a nice judo move on the attackers’ part. By making the countermeasure the target, it will make everyone in the line at least as jumpy, nervous and generally suspicious-looking as the average “hinky” acting terrorist.

Last weekend, after Lollapalooza, about 900 people were queued up at Union Station in Chicago, waiting for a Metra train out to the ‘burbs. Unlike normal “crowded times”, like, say 17:30 on a weekday, the Railroad Police kept the doors to the platform shut, so that rather than allowing people to go onto the platform and board the waiting train as they arrived, the aforementioned build-up of nearly 1K people in an enclosed area was allowed to occur. Why this was done, I have no idea, but I have seen it more than once. Next time, I’m going to ask one of the cops what the point is. It’s not like there’s any other way to get onto the train, so why make everybody go through the choke point in a 10-minute interval?