What's that supposed to illustrate? That a bomb in a crowded place can be harmful? Hmm, ok, better get the TSA to cordon off all malls, clubs, popular restaurants...
The thing about air travel is that there is a better argument for (some) security to prevent hijackings and bombs, both because planes are very fragile (there's a decent chance for a smallish bomb to result in the entire plane being lost and all passengers killed), and because they're usable as missiles against much larger targets (as illustrated by 9.11). Planes, in other words, have a somewhat unique ability to magnify the effect of a given terrorist attack.
None of that is the case for rail transport. For the most part, a train is simply a very crowded place, in a society that's absolutely chock-full of very crowded places. Indeed, the long-distance/regional trains most likely to receive TSA "attention" are much less crowded than local trains and subways which will almost certainly never be allowed to fall under TSA control for practical reasons.
The security checks at airports serve very little use in preventing the destruction (through a small explosion) of an aeroplane, given that after going through the security checks it is perfectly trivial to buy large quantities of pressurised containers and accelerants.
On the other hand making sure no one has guns on a plane seems worth queueing at the metal detectors for. Maybe that is just me being anti-gun though...
You're assuming that protecting people from terrorism is actually a primary motivation of these measures, and that powerful police institutions might might give up a chance at increased control of the population, which makes their jobs easier, for the sake of efficiency.
If you give the police free reign, you'll end up with a society that's only efficient for the police.
What's that supposed to illustrate? That a bomb in a crowded place can be harmful? Hmm, ok, better get the TSA to cordon off all malls, clubs, popular restaurants...
The thing about air travel is that there is a better argument for (some) security to prevent hijackings and bombs, both because planes are very fragile (there's a decent chance for a smallish bomb to result in the entire plane being lost and all passengers killed), and because they're usable as missiles against much larger targets (as illustrated by 9.11). Planes, in other words, have a somewhat unique ability to magnify the effect of a given terrorist attack.
None of that is the case for rail transport. For the most part, a train is simply a very crowded place, in a society that's absolutely chock-full of very crowded places. Indeed, the long-distance/regional trains most likely to receive TSA "attention" are much less crowded than local trains and subways which will almost certainly never be allowed to fall under TSA control for practical reasons.