"Do you know how fast you were going?" the officer asked.
"Yes, I was going 90," she replied.
"The speed limit here is 65!" the officer told her.
"Oooooh," she said. "I've been following the blue signs ..."
"What? That's the interstate number!" exclaimeded the officer incredulously.
"Oh, dear," said the old lady.
At this point, the officer looks at the occupants of the car, three other little old ladies, all of whom look incredibly tense, with their eyes bugging out of their heads, clutching their purses like their lives depend on it.
"What's wrong with them?" he asked.
"Ah, hm," said the old lady thoughtfully. "Well, it would seem we just got off Route 128."
(Boston geography, but funny, I hope, nonetheless.)