A semi-trailer truck (also called a semi or 18-wheeler) is a long haul truck that typically consists of a tractor unit and one, or more, trailers. They are the largest trucks on the road and can weigh up to 80,000 pounds (36,000 kg). The average length of a semi-trailer is 53 feet (16 m), but they can be as long as 91 feet (28 m). Semi-trailers usually have anywhere from four to eight axles depending on their size and weight.
Most soybean trailers hold between 48,000 and 52,000 bushels. This range varies based on the trailer's size and axle configuration. For example, a smaller trailer with four axles may only be able to hold 48,000 bushels whereas a larger trailer with eight axles could potentially hold up to 52,000 bushels.