One of the large vehicles you might see on a construction site or road crew is a steamroller, which uses a large, heavy cylinder to smooth the surface of a road or other paved area. Be sure to stay out of its way!
Many people use the word steamroller to mean "road roller," although strictly speaking that's incorrect, since these modern vehicles aren't powered by a steam engine. A true steamroller had a smokebox and chimney, and the steam it produced enabled it to move forward as it rolled and compressed the surface below. Used figuratively, steamroller means something or someone that moves forward relentlessly, without regard for anyone who happens to be in its way.