> atleast there might be less gridlock
I've never lived in a hurricane area, but when I think of news coverage of problematic evacuations, they're showing people stuck on highways, not people stuck in urban traffic grids.
It's a throughput problem. Computer controlled "car trains" with shorter following distances can boost traffic throughput, but I don't think that would be enough to make evacuation of large cities actually feasible. The highway system is simply not built for that use case. Especially since evacuation often occurs during inclement weather that reduces capacity.
AFAIK, most places try to figure out how to make shelter in place work, because mass evacuation is likely to end up with many people facing the weather event while on the highway.
You could theoretically do better with busses and trains, things, but there's likely not enough busses that are setup for long distance travel available: lots of municipal bus fleets are setup for alternate fuels which is great for emissions but makes it hard to travel to a neighboring state, because there may not be appropriate fueling opportunities on the way. Etc, etc.
I’m from a flood prone, hurricane prone area - there were some painful lessons from Hurricane Andrew, famously the hurricane tie system for buildings in Florida which quickly spread, but in South Carolina they also learned a very important lesson - reverse all lanes on the interstate so everyone can flee as quickly as possible. The “stuck on I-26” problem no longer exists. I’ve personally driven 100+ miles in “the wrong way” to evacuate. It’s quite fun. They also perform statewide annual drills to make sure all emergency staff can faithfully execute this reversal pattern.
Do other states not do this?