The Emanuel administration might talk to Lior Strahilevitz, a young star at the University of Chicago Law School. He is an expert on property law, privacy law and traffic safety, and recently lectured on his germane new book, “Information and Exclusion” (Yale University Press).

For sure, use technology to save lives and prevent traffic accidents, Mr. Strahilevitz said. But also do the following:

Collect only information essential to traffic safety enforcement, programming cameras to blur a driver’s image. Limit how long information is kept, perhaps purging files every 30 or 60 days. Make most cameras as visible as possible. Curb the merging of disparate databases or their sale to private companies for other purposes. And restrict the public availability of data, because information that was anonymous when published can be tied to specific individuals years later as data mining improves.

It’s an intrusive era. Insurers know that those who buy felt pads to place under table legs to avoid scratching floors are obsessives who pay their bills on time; clerks may soon not ask if you’re just browsing since they’ll know your tendency via biometrics; and tracking data can discern your politics and whether you see a psychiatrist or frequent a casino.

“The thought of Richard Nixon having access to the sort of data now available to government should make anyone shudder,” Mr. Strahilevitz said.

And data security is only as reliable as the weakest human link in the surveillance chain. Just consider how it is that Pfc. Bradley Manning, a low-level Army intelligence analyst, is accused of transferring those prodigious government files to WikiLeaks.

At the Green Line stop, the Missile exuded justified confidence, especially given recent victories, like sweet-talking a somewhat wimpy City Council to pass his budget unanimously.

He is well seasoned too in massaging the national news media, with a journalist in tow being given access for a profile in The Atlantic.