When the Three Mile Island nuclear generating station along the Susquehanna River seemed on the verge of a full meltdown in March 1979, Gov. Richard L. Thornburgh of Pennsylvania asked a trusted aide to make sure that the evacuation plans for the surrounding counties would work.
The aide came back ashen faced. Dauphin County, on the eastern shore of the river, planned to send its populace west to safety over the Harvey Taylor Bridge.
“All well and good,” Mr. Thornburgh said in a recent speech, “except for the fact that Cumberland County on the west shore of the river had adopted an evacuation plan that would funnel all exiting traffic eastbound over — you guessed it — the same Harvey Taylor Bridge.”
Nearly 250,000 people would have been sent in opposite directions over the same narrow bridge.
There seem to be some coordination issues to resolve, among other things. Transportation infrastructure isn't built to accommodate everyone leaving town at the same time.