And, having lived on the Cape for 26 years, I can tell you that there were periodic articles in the Cape Cod Times about the "evacuation plans" for the Cape in case of an accident at the Plymouth power plant.
Locals would break into howls of laughter about the latest "plan."
Cape Cod is a peninsula with 2 bridges for egress. On a typical summer weekend, they're nothing but a huge parking lot. 5-hour delays getting over the bridge are routine on holiday weekends, with traffic backed up 20 miles or so.
It was conventional wisdom on the Cape that if something cataclysmic did happen, your best bet was to head for the waterfront and a boat, NOT the bridges.
If you didn't own a boat or had a friend that did - Sayonara.