Evacuating a huge number of people is a nightmare, and I don't think anyone expected the storm to stall and dump the amount of rain that it did. Many people have been injured or died in the past because they were stuck on the road trying to evacuate.
I am a Florida girl and I have been through more hurricanes that I can remember. Evacuation has to be done in stages and not everyone wants to leave when told. I lived in the Tampa Bay area in 2004 and they had an evacuation plan that works as well as any I have seen. Coastal residents are first and they are told to go a few days ahead of the storm. Next is those in the low lying areas a bit more inland. They also evacuate nursing homes and medical facilities with the first wave. I believe there are 4 evacuation zones in all. It helps to prevent the gridlock by not having everyone leave at once. Getting back after a storm was always worse then evacuating.
I don't think I have ever heard of any other place using such a plan. I hope Houston has learned where their problem areas are by now, as they did have flooding last year as well, just not to the same extent. I would hope they can develop a zoned evacuation plan and implement it in the future.
And even if you evacuate, you still may not be safe. I have an RV and evacuated ahead of Irma. The storm shifted and where I had planned to wait out the storm was now in the path. I moved to another campground and was still in the path. I moved again. (I swear that storm was stalking me.) I finally ended up in TN at a relative's house and waited it out. By the time it got to me it was just a rain event, but now I was much farther from home than I wanted to be. I waited an extra day before coming home because I knew there would be gridlock and the gas supply would still be low.