This revision reduces the complexity of this practice by simplifying the General Package Factor (G) equation, clarifying conditions for using restrained and unrestrained reach tables, removing English unit tables, clarifying the G value boundaries between each reach table, describing in more detail how to interpret when a control is considered within reach, and limiting application of the practice to Class A vehicles.
The substantial simplification of the General Package Factor (G) equation (from 7 vehicle dimensions to 2) occurred as a result of a statistical investigation begun in 1997 by members of the SAE HADD committee.
A stepwise regression analysis was conducted on a data set of 81 vehicles spanning model years 1997 – 2005. The H30 dimensions were typical of passenger cars and light trucks, ranging from 188 mm to 374 mm. Heavy truck packaging data were not available to include in the analysis. Most of the vehicles in the dataset had reach zones identified by reach tables 4, 7, 10 in this document. It was determined for each vehicle that a significantly similar G value could be obtained from only two package variables, H30 and H17. The H17 dimension was found to be the best predictor for cars, while H30 was the best predictor for trucks and vans and for all vehicle types combined. The output of this simplified equation (Figure 3) fit the G values from the original equation with an R2 of 0.96, while the same reach table was selected for 93% of the vehicles. Based on this result, the committee adopted the simplified equation for G.