The key for those living in urban areas would be to drive out well before the possibility of WWIII became imminent. This senior is much more flexible versus those tied to working jobs with kids in schools etc so would leave my core urban area at a low threshold towards the north coast if the threat rose.
Once situations become serious with panic setting in, one can expect major freeways will quickly be blocked and those living in more rural areas will make sure their roads leading in will be blocked so massive hoards from urban areas don't inundate them and what store supplies they may have locally. Since the Internet will go down, only those with small scale paper or device digital maps and rural locals will be able to navigate more freely.
One can download this highly recommended
86 minute long 2010 documentary mpeg video,
After Armageddon, from the following website that was a bit less than 400 megabytes, so took about 5 minutes to do so. If so, most people, especially in urban regions, will be unprepared and likely die in just a short few weeks. They will die from starvation, murder by desperate others, and criminal armed gangs, seeking food, guns and ammunition, water, gold, gasoline, and attractive women. So wise choice will be to leave early.
After Armageddon : Free Download, Borrow, and Streaming : Internet Archive