Transportation is not only the most public aspect of log extraction from the woods, but it is also the most expensive—and often limiting—step for the logging contractor. This project focused on the potential efficiency gains of fully loading trucks on a more consistent basis. Legal and corporate mill restrictions confine the weights that raw material transporters can haul. Hauling the maximum legal load every trip is the most cost efficient method of transporting raw materials.

We collected load data from forest products companies that are members of the Wood Supply Research Institute (WSRI) and analyzed weight data from twenty-four mills. We compared the mean gross vehicle weight (GVW) at each mill to the federal weight limit of 40 tons and to any mill overweight policy. A benchmark group of suppliers was identified at each mill as the five with the lowest coefficient of variation (CV) on their gross vehicle weights to compare to the other suppliers at each mill. Three relationships involving tare weight were tested: the relationship between tare weight variability and GVW variability, the relationship between tare weight and variability of payload, and the relationship between tare weight and net weight. The last part of the study estimated the potential cost savings of reducing load variability.

All mills had mean GVW significantly different from the federal limit at the 90% confidence level or stronger. A majority of loads delivered to each mill (77-100%) complied with mill GVW policies. At most mills, the benchmark group had higher mean GVW and net weights, as well as lower GVW variability. Decreased GVW variability was associated with higher payloads (Figure 1). Mean tare weight and mean net weight exhibited an approximate 1:1 relationship at 15 mills (Figure 2). Benchmark groups at 14 mills had significantly larger payloads and we project had 4 to 14% lower per ton hauling costs than other suppliers at the mills. Operating at the reduced variability level of the benchmark groups across the 221 million tons of roundwood annually consumed in the U.S. South suggests potential savings of $100 million are available.

Figure 1. Relationship between gross vehicle weight variability and payload.

Figure 2. Relationship of tare weight to net weight.

For a more in-depth report, see Center for Forest Business Research Note #20, and Forest Resources Association Technical Releases 06-R-20 and 06-R-21.