I live in southern NJ outside of Philadelphia. As I've tried to explain to my wife, and as anyone can surmise from a brief look at a map, New Jersey is a peninsula. In the event of a major catastrophe that would require evacuation from the area, it is highly likely that all means of egress from the state would be either disabled or severely congested, other than marine transportation.

The major routes of exit from southern NJ are the Delaware Memorial Bridge, the Commodore Barry Bridge, the Walt Whitman Bridge, the Tacony-Palmyra Bridge, the Betsy Ross Bridge, the NJ/PA Turnpike bridge, and the Burlington-Bristol Bridge. Most of these bridges will put you in heavily urbanized areas of the Philadelphia metro area, increasing the possibility of jumping from the frying pan into the fire, so to speak. Further north, there are a collection of bridges from the Trenton, NJ area north, most of which are two lane bridges. It's not likely that a large population could easily traverse these bridges without complications, and the farther south one goes increases the difficulty of reaching these exits.

To top all this off, southern NJ is home to several major military installations (Fort Monmouth, Fort Dix, Earle Naval Weapons depot, McGuire AFB, FAA Tech Center [outside of Atlantic City], etc), as well as being generally surrounded by the Philadelphia and (further north) New York City metropolitan areas, and other important sites that might be the object of terrorist interest. I have to say, I'm quite surprised that there has not yet been a terrorist incident in Philadelphia, considering the psychological impact of the historical sites residing there.

My preferred solution would be to move away from the area entirely, but the decision is not only my own to make.

That said, there is always the possibility of a less severe type of emergency that might require a more localized evacuation, so it would only be prudent to be prepared for such things. For example, hurricane evacuations along the NJ Atlantic shore are not all that uncommon, and I still recall a local evacuation when I was a college student in Pittsburgh that was the result of a chemical spill caused by a train derailment.

While the spectre of emergencies is of somewhat more concern to my fellow New Jerseyans in the northeastern part of the state abutting New York City, available evacuation routes over land are a bit more numerous and accessible. Evacuation to the west and northwest to Pennsylvania and/or upstate New York is slightly more feasible. Of course, the population density is even higher in that area, and New Jersey, overall, still boasts(?) the highest poulation density in the nation, as far as I am aware.

It is possible that staying put might be the more prudent course in any particular hypothetical situation. However, many of the things you might want to include as part of your preparations for stay-home survival will also be of use should you choose to evacuate.