Last night I was driving from Harrisburg to Lewisburg,Pa.,a distance of about eighty miles.It was late.I was late and if anyone asked me how fast I was driving,I'd have to plead1) the Fifth Amendment2) to avoid self-incrimination3).Several times I got stuck behind a slow-moving truck on a narrow road with a solid white line on my left,and I was clinching my fists with impatience.