At a construction site where fill soil was being placed, several dump trucks were tipping soil. One after another, the front ends of several trucks tilted upward—apparently because, when the soil was being dumped, the earth slid down and the drivers failed to operate properly or coordinate well enough, so the vehicles were not driven away in time. With more than half a load of soil still pressing down on the rear, the center of gravity shifted backward, causing the front ends to lift up and the trucks to become stuck fast. The drivers, sitting in the tilted cabs, could do nothing about it and had to let an excavator standing nearby scrape the soil off the trucks and give them a push before they could be freed. There was once a truck still stuck with its front end up when another truck drove over to dump soil, and as a result both trucks tilted up at the same time, creating a unique sight at the site.