Re: Wow. This is like software failure mode bingo. I call "HOUSE"
And yes, despite it's snore inducingly dull subject (traffic) there are bad people who can find a use for this technology.
Sure. It's useful as a low-sustained-cost terror attack, for example: snarl up traffic (significantly worse than normal) for many days in a row in an urban center.
Low-sustained-cost is actually a successful terrorism strategy. The IRA used it for years to bolster their position so they could run an extortion racket, among other organized-crime goodies, and then leveraged it to claim legitimated political power. Muhammad & Malvo used it to scare the crap out of D.C. residents for three weeks, and they could have continued doing so for years (particularly if they periodically moved on to a new city) had they not gotten greedy and lazy.
There are lots of potential LSC terror projects. Arson of abandoned (and thus poorly defended) buildings is another; free-range arson was a big contributor to the gutting of Detroit.
Compared to bombings, sniping, and arson, fucking with traffic doesn't seem like much - unless you're depending on an emergency vehicle, perhaps. But that kind of widespread, low-level cost really eats away at a locality's civil society and ability to make rational group decisions (often pretty low to begin with). And note the asymmetry: it's nearly zero cost for the attacker, assuming we have a high density of vulnerable "smart" intersections in the metro core.
In fact, what this sort of thing shows is that "terror masterminds" are much rarer than the government scaremongers would have us believe. Terrorist organizations are generally far more successful with this sort of strategy than with plowing lots of resources into splashy attacks with a high probability of failure.