Anyone who travels on (or more accurately, parks on) Mopac, IH-35, or Austin's other "freeways" is familiar with several concepts: frustration, road rage, more frustration, stupidity, and more frustration.
There is one question that no one can answer. Why does traffic on these "expressways" frequently come to a complete halt. Yes... occasionally, there's a reason. An accident has bottle-necked two lanes into one. A stalled car, or other road hazard slows traffic.