Bssss, on the bug out. No one with any brain will get on the highways in a bug out, you may get 1/2 mile from home when some crazy will slam dunk you , no one running from any terror will survive the Highways.
In a city there are areas for survival------London subway tunnels for example.-----A bug out bag is use full only when one finds a place to get underground .
Plenty of places in the big city's to find older buildings with deep cellars and especially banks that store vaults down there.
We up here, are close enough to the old Air Force Sac base to walk or run to the safe havens left when the base closed down. The hospital that is now used for a College that has been said to with stand a bomb blast. I do wonder what is underground in that place. First place I would head for in a time of panic and insanity.
In a terror operation or a man made problem say a power plant exploding, one does not want to be above ground driving in a sea of terrorized people.
This is much like the people driving down the road in tornado season. We are told to get below ground, in a ditch, or cellar. Those that head for the underpasses, some do survive as others are not so lucky and sucked out by the wind.