[grandalf]

In terms of the potential for economic damage, a full-fledged bioweapon attack is not all that much more effective than a low-sophistication attack (or several, staged at the same time).

So while it is useful to understand the way subway systems may disperse particles, this kind of research does not reduce the risk of economic damage from low-sophistication attacks targeted at the subway system.

It is difficult to obtain Anthrax or similar chemical agents, and the number of people needed to pull off a successful attack is fairly large. Machine guns or simple explosives (like those used in the Boston Marathon attack), however, are 100x more likely to succeed and cause the intended economic damage, so long as they either create a fear of traveling by subway or lead to security checkpoints that drastically reduce the subway's throughput.

The key takeaway, in my opinion, is that nobody with access to the NYC subway really wishes to harm it or do terrorism.

[jorblumesea]

Fear is a huge part of any terrorist endeavor and small invisible particles killing you while you commute is far scarier than someone with conventional arms. Further, NYC subways would be closed for weeks, the US's largest city and an economic powerhouse would grind to a halt. The economic damage is such an event would be huge.

[grandalf]

It would be very easy for a single unskilled attacker to kill upwards of 20 people using a conventional firearm or stuff that can be found at any hardware store.

I'd estimate that such an attack would result in the subway being closed for weeks, particularly if several happened successfully a few days apart.

Similarly, small explosions dispersing any remotely harmful smoke or chemicals (even chemicals that are easy to obtain) would be amplified by media coverage, and politicians would close the subways as a knee-jerk response.

Sure, an actual banned bioweapon/chemical would be worse, but my point is that terrorism (the tactic not the alleged existential threat) works because it requires little skill, technology, or access to difficult-to-obtain materials to create fear.

[gcr]

Today, right now, there already are terrible biohazards on every subway car. Have you ever touched one of those poles? Truly frightening.

They say you're not a "real New Yorker" (whatever that means) until you've lost a finger to the subway pole bacteria...

[ethanbond]

Why are you framing the loss of life solely and exclusively within the bounds of economic damage?

Obviously there are cheaper ways to cause more expensive damage. That's not what terrorists care about and that's not what potential victims of terrorism care about.

[grandalf]

The point of a terrorist attack on the subway would be to get the subway closed for a while. Every day it is closed, the city suffers economic damage.

The point of a terrorist act causing loss of life is to create the fear that will cause economic damage, not to somehow wipe out lots of civilians.

In a war, the willingness to kill civilians is proportional to the need to do so to make an impact on the opponent's will to fight. Obviously nobody would prefer to kill civilians over combatants, but all militaries will do it without hesitation if circumstances dictate.