Moving 1.5 million people is really hard. While running some errands today, including trying to get some gas, two gas stations were empty. I heard on the radio how one lady had been and still was on I45 for 18 hours and she hadn't even left Houston city limits yet, they are more then a little worried about riding our the hurricane in their car.
Riding a Cat4 out in your own home is one thing, doing it sitting in your car parked on the Interstate is quite another.
There are going to be several lessons learned from this, probably the wrong ones.
If there are large numbers of deaths due to people being stuck in their cars during landfall, then people will learn that they are better off staying at home then leaving during a mandatory evacuation. This is the wrong lesson the right lesson is to leave before the mandatory evacuation order comes down so you can use the roads. Make your decision 72 hours before projected landfall and you should be fine.
Another better lesson to learn is to plan your escape route such that you do not use the Interstate, everyone who doesn't plan ahead will use the first idea that pops into their head and the Interstate will be number one on the hit parade. I would not be surprised at all if the county roads and state highways are basically empty right now all around Houston.
If you are prepared you will not fear. I already have scoped out some state highways that will get us a long way from here in case of an evacuation. You should do the same before the disaster comes to you.