Off-Highway Trucks: How to Calculate Truck Fleet Requirements

The number of trucks required to perform a certain task is a function of the productive capability of one independent truck and the total tonnage required. Hourly productive capability of one truck is the product of trips, or cycles, per operating hour and effective payload. One cycle is made up of load, dump, and travel time, the sum of which comprises theoretical cycle time. This time is then derated by a productivity factor, giving an average effective cycle time which is used to calculate the number of cycles per hour. Rated payload is the truck's designed tonnage, while effective payload is the average amount that is actually carried. Manufacturers, particularly of the larger trucks, produce various body sizes designed to carry materials of different densities. However, it is not always possible to carry the rated payload because the material might be lighter than expected, a body of the required size cannot be produced, or because of spillage on particularly steep grades.