Charles,

I happened to be driving behind a 18-wheeler this morning, and on the back was painted "great pay $0.40/mile" and I was surprised since I recall seeing much lower amounts.

Now since this truck driver makes $100.000 he must drive 100.000/0.40 = 250.000 miles every year.
assumong he takes weekends that gives ~250 working days at 1000 miles/day. Now let us assume he actually drives for 10 hours every day (The law does not allow driving a truck while tired) that makes him drive at a speed of 100 miles per hour.

The above calculations are erroneous because they do not take into account the frequent and lenghty layovers a trucker has waiting for next load to be ready.

Erik