One of the lessons taken from New Orleans was that people would simply refuse to evacuate if you made them leave their pets behind. FEMA has now changed its guidelines accordingly. The idea that people would be forced to evacuate without their children is more than a little unrealistic.
In '75, I was caught downtown by an unexpected/underestimated snow storm. Then, there were lanes that were switched for each rush hour. Traffic was so tied up, it took almost an hour to get from the city parking lot on Michigan over to the Drive. (I was too stupid to turn around and stay at the Palmer House.) Traffic going north took over ALL the lanes of the Drive. Folks were exiting via entrance ramps. (I have no idea what southbound traffic did).
I can say that, even with all LSD lanes going north, traffic still ground to a halt. Even though I lived further north, I gave up and exited around Fullerton. Shortly thereafter, my car battery died–because traffic moved so slowly that the car ran on battery power until it died.
So, even giving over all lanes to the exit direction wouldn’t, I don’t think, keep traffic moving. My opinion is that police are rarely proactive clearing routine traffic jams–I don’t think for a minute that there’s a plan that police are ready to follow that would keep traffic moving in a crisis.
I am back to my basement and that hand-cranked radio. Maybe I should stock up some candles and one of those books I know I should read, but never had the time to.
Just be sure to include a spare set of eyeglasses.
I actually like that idea. I’m walking distance from the north branch of the river. I’ll have to see if there is an inflatable boat on sale at CostCo.
I live north of the city but very near Lake Michigan. Wouldn’t it be relatively easy to evacuate via the Lake? You could flee all the way to the Atlantic Ocean, or just go Up North.
This is assuming you had access to a boat, of course. There are plenty of boats in these parts.
I saw that episode of the Twilight Zone…maybe heading to the nearest bank vault isn’t a bad idea.
You do realize that if the building collapsed you’d most likely end up trapped in the vaul until archaeologists found you. 
I would like to point out a couple flaws in thinking I see here.
First, a lot depends on how much time you have to evacuate. There’s a huge difference between, say, a hurricane where you have days of warning and something more immediate, like an earthquake or attack. The more time you have to evacuate the more orderly and effective any attempt will be.
Second, there have been occasions in the past where part of Chicago was evacuated, or at least had the population significantly reduced in a short time period.
One was the Chicago Loop Flood on April 13, 1992. At a certain point the city decided to shut down power to the Loop and asked that people working there go home, relocated vulnerable people (elderly, disabled) to other locations, and so forth. Extra buses were provided, and as I recall while mass transit and the roads were crowded it was pretty orderly and no panic ensued.
Another was on September 11, 2001. The downtown skyscrapers emptied out spontaneously as employers let their employees go home and/or people decided they were going home, permission or no. At least on the South Shore Line they threw the schedules out the window and simply loaded the trains and sent them out when they were full. I did not note any signs of panic, although, with Loop train stations often being located under skyscrapers there was certainly some stress.
So, based on that, at least in Chicago, I would expect that the various mass transit agencies would do their best to get people out of the downtown areas as quickly as possible. As noted, freeways can be made one-way on both sides. With enough lead time you can evacuate a city in sections so the roads/rails don’t get gridlocked.
New Orleans prior to Katrina also saw tens of thousands of people leaving the city without panic or crisis. Yes, there were people left in the city (who had trusted in shelters like the Superdome and did not expect society to abandon them there) but most of the city did, in fact, leave.
Now, would any city be COMPLETELY evacuated? No, probably not. The disabled and poor are less able to get themselves out. There will always be a stubborn stay-put element. But you can certainly get a lot of a city evacuated, most of the people, and that would certainly be worthwhile. Panic will not necessarily ensue, though of course it is a risk.
Again, a lot depends on whether you’re evacuating before a catastrophe or during/after one. Obviously, the before evacuation has the advantage of intact infrastructure. Of course, there will be problems even the most orderly evacuation but that doesn’t mean it’s a failure.
There’s some precedent; they tried to evacuate Houston in 2005 in the shadow of Katrina, when Hurricane Rita was bearing down on that area as a Category 4 or 5 storm.