Chernobyl, Fukashima and New Orleans (Katrina) are great classic examples of unpreparedness and denial on a large scale.
In the case of Chernobyl there was no warning of course, and so the USSR had to use busses to get the people to bug out fairly quickly, within a day or two. The initial denial then was on the part of the plant managers and the government. But eventually the USSR had to act, since they understand nuclear contamination better than anyone.
In the case of Fukashima there was about half an hour of warning between the quake and the tsunami. That's about how long it would take me to load everything into my SUV if I hurry it -- maybe 15 minutes if I really hurry it. Once again, the plant managers and the government played down the seriousness with a denial strategy.
In the case of New Orleans (Katrina) there was lots and lots of warning, with millions of people ignoring the danger completely, and many waiting until the last minute. The highway jam-up is going to be the recurring snafu in cases like that because people drive like idiots and have accidents all the time. And they are not even smart enough to get their own crashed rigs out of the way by themselves, they just sit there and wait for the highway patrol and a tow truck. Again, there was denial on the part of the government, and the people were again left to themselves. Even worse this time, some bozo mayor decided to send the police around to collect everyone's guns from them.
New Orleans was as close to a simulation of a complete zombie bugging-out scenario as there has been in a long time. And approaching storms are usually the reason why. I don't live in a hurricane zone; if I did, I would be bugging out every time one got close like that. My toughest personal experience was 3 days of sheltering in place after the 1989 Loma Prieta quake.
During the 1989 quake here, I was living in a villa style apartment complex, with a central grassy quad in the middle of it. One of the neighbors organized a bbq in the grassy quad for everyone to bring their own meat from their freezers before it spoiled. It was great fun. I cooked up and served white rice for everybody, in a Rice A Roni style with bouillon broth -- it tastes pretty good like that.
Everyone was happy and we sheltered in place for 3 days like that until the collapsed freeways were dealt with, and commerce could get back into our areas. I had plenty of rice left over after feeding everyone for 3 days.