Are you a Big-Rig Hypermiler ?...

[Chamberpains]

200 x 50 week work year = $10,000 bonus in fuel savings. There are also thousands of hard to calculate savings in wear and tear on the truck that is not happening. Down time not spent in a shop. It's a real huge pay raise just to loose a few minutes an hour on travel time.

Less stress of trying to pass traffic and fight your way around everyone all day is more than enough to justify slowing down. But the $$ in the pocket is just more incentive.