"...requiring Interstate gas stations...to double the size of their fuel storage tanks??..."

That wouldn't make enough difference. I used to have to stand out on I-5 in central CA on the Wed. before Thanksgiving and the Sunday after (the two heaviest traffic days of the year), directing traffic off of the frwy and back on at one of the main fuel stops for about a hundred hundred miles. Every station there had tankers coming in several times a day, trying to keep up, and that was nothing like a mass evacuation. In a real traffic jams the tankers would be jammed up with everyone else...