Has there ever been, or a study done, of the mechanics of a evacuation of a major city? I'm mostly interested in how many people flee, how many stay, and how many people try the main roads out, and how many go for secondary routes.
All of the major cities have done studies and have their own plans. Some I've heard of include emptying certain areas first to allow other areas to more effectively pass, or of evacuating by order according to the first letter of their last name. None of them can be evacuated very quickly. Especially when you consider the number of morons who normally drive around with 2 gallons of fuel in the tank, running out of fuel on the freeway and clogging it up for everyone else. There's simply no excuse for that. It costs the same to keep a tank full as it does to keep it empty.
There's no quick way out in an evacuation other than getting out before it starts. Or to be the first car on the road when the order is given, and only if you live near the edge of the city. Those in the middle of it are screwed.
I've always said keep your eyes and ears open and be ready to go at a moment's notice. If it looks bad, bail. Don't "wait and see". Better to have a few false starts than a single late one. If you want to "wait and see", drive out of town, pull over and listen to the radio or something. At least you're out of the traffic jams if it starts up, and you have a headstart.
Whole city evacuations are a mess. It can be done but its painfully slow. The best way to evacuate is by the waterways. Leave the car and take the boat. No red lights or traffic jams. The down side is you need transportation on the other end. My evac plan for years from New Orleans when I lived there was by the Mississippi River. Roads are useless in a crisis.
In Katrina a good 95% of people left. The people you saw on tv were a fraction of the total New Orleans population. Every road out was full. Every lane was full (even the sides of the road) and both directions were now forced in one direction which was out. Many ran out of gas which slowed progress further. It took us 6 hours to drive a distance that normally took 35-45 minutes.
When a mass exodus happens you either have to have seen it coming and left early, or bug in until the exodus is mostly over. Allowing you to move quicker, otherwise you will be stuck with all the other sheeple. If that happens you better look like the rest of them, cause a bug out vehicle full of water and gas won't stand up long against the mob.
it is important to remember that a certain percentage of people will refuse to leave. As in Katrina, a lot of the ones that stayed had plans on looting and stealing. Of course there were others that were unable to leave.