Probably true. In most cases, escape from the city even with a full tank and extra fuel will be frustrated by all the wrecks and roving gangs. I was talking to a former resident of Denver who moved down here and his plan before was to get on his motorcycle with his wife and escape Denver. I asked him one question which really highlighted the silliness of his previous idea .... what if it happens after a normal 2 foot snow fall? At least he had the sense to move out last year.
A two foot snowfall would probably make escape on a snowmobile easier — little competing traffic, and lots of alternatives to the streets.