Back It In

What it models

The yard is drawn to scale. The trailer is 53 feet long and 102 inches wide. The dock door is about nine and a half feet, so a centered trailer has six inches to spare on each side, and the doors sit on 12-foot centers. The truck and trailer move the way a real rig does at walking speed: the tractor pivots on its drive axles, the trailer pivots on the fifth wheel, and the trailer's wheels can only roll the way they point. That is the whole reason backing is hard. In reverse the trailer goes the opposite way to the wheel, and a small swing grows on its own until you steer against it.

What it does not model

It is a simple model. Tires never slip, the ground is flat, nothing has weight, and the steering answers instantly. The mirrors are flat views of the yard from above, not true mirror optics. The 80 degree jackknife limit, the speeds and the scoring are our choices, not a driving test standard. The two 90 degree maneuvers can be finished, and we checked that by letting a script drive them, but the script needed to pull forward first, the same as a driver does.

Why a software firm built this

Receiving and shipping run through a dock. While a trailer is being straightened, the door is blocked and the crew behind it waits, and that time rarely shows up on any report. A few tries in this simulator is a quick way to show a team why a yard schedule needs slack in it.