Research, Development, and Application of Methods to Update Freight Analysis Framework Out-of-Scope Commodity Flow Data and Truck Payload Factors
Appendix D. Example Calculation of Revised Payload Factors
This appendix works through, using Standard Classification of Transported Goods (SCTG) 20, Basic Chemicals, which is Vehicle Inventory and Use Survey (VIUS) Commodity 5 as an example, the steps in chapter 12.
In the 2002 VIUS Microdata, there is a record for a tractor trailer, i.e., Combination Unit truck, where the Principal Product Carried is reported as Powered Tools, which are carried in 60 percent of its miles, but 25 percent of the miles are reported to be carrying Basic Chemicals. The weighted expanded annual miles reported for this record is 8,758,553 which means that 2,189,638.25 miles would be carrying Basic Chemicals.
For the previous payload factors, this record would NOT have contributed to the payload factors because these values were only computed for the Principal Product Carried.
That 2002 VIUS record reports an average loaded weight of 78,000 lbs. and an empty weight of 33,500 lbs. which implies that the average payload is 44,500 lbs. This also means that the annual ton-miles carrying Basic Chemicals is 48,719,451.
These are figure 70 and figure 71 in the main body of the report. For that record, the original payload factor for SCTG 20 would be 22.25 tons per truck.
By summing all records by truck size and commodity in the 2002 VIUS microdata the sum of the miles and ton-miles are as shown in table 55. Single unit (SU) trucks are Strata 3 and 4 in VIUS. Combination unit (CU) trucks are stratum 5 in VIUS. The Combination of SU and CU trucks is the sum of these three strata. Also shown in the table is the standard error for each calculation, from the standard deviation, count and means of the records. The results also can be used to compute the share of the ton-miles for SU and CU trucks.
Table 55. 2002 vehicle inventory and use survey results for standard classification of transported goods 20.
 |
Annual (Billions) |
Standard Error |
| Ton-miles SU, 2002 |
1.19 |
17.6% |
| Miles SU, 2002 |
0.29 |
13.0% |
| Truck Payload Factors (TPF) SU, 2002 (tons per truck) |
4.10 |
21.9% |
| Ton-miles CU, 2002 |
10.48 |
6.7% |
| Miles CU, 2002 |
0.53 |
10.0% |
| TPF CU, 2002 (tons per truck) |
19.77 |
12.0% |
| Ton-miles SU and CU, 2002 |
11.67 |
12.3% |
| Miles SU and CU, 2002 |
0.83 |
16.0% |
| TPF SU and CU, 2002 (tons per truck) |
14.06 |
20.2% |
| SU Share of Ton-miles, 2002 |
10.2% |
|
| CU Share of Ton-miles, 2002 |
89.8% |
|
(Source: Federal Highway Administration.)
From Highway Statistics table VM-1, it is possible to determine the ratio of TOTAL annual Miles for SU and CU trucks from 2012 to 2002. By summarizing the results from Vehicle Travel Information System (VTRIS) table W-3, it is possible to determine the ratios of payload weights from 2012 to 2002. There is no source to show how these values have changed by commodity. By assuming that the ratios can be applied to every SCTG2 value, the 2012 VIUS for SCTG 20 values can be computed. The ratios from VM-1 and W-3 are shown in table 56 .
Table 56. Ratio of miles and weights 2012 to 2002.
| a= Ratio SU miles 2012 to 2002 |
1.39 |
| b= Ratio CU miles 2012 to 2002 |
1.18 |
| c= Ratio SU payload weights 2012 to 2002 |
1.199 |
| d= Ratio CU payload weights 2012 to 2002 |
1.011 |
(Source: Federal Highway Administration.)
The 2012 ton-miles would be the 2002 ton-miles multiplied by the change in weight, c for SU trucks and d for CU trucks, multiplied by the change in miles, a for SU truck and b for CU trucks, where a, b, c, and d, are from table 56 and the 2002 ton-miles are from table 55. The 2012 miles would be the 2002 miles multiplied by the change in miles, a for SU truck and b for CU trucks, where a and b, are from table 56 and the 2002 miles are from table 55. The 2012 tons and ton miles are shown in table 57. The 2012 miles for SU trucks are according to figure 73. The 2012 miles for CU trucks are according to figure 74. The 2012 ton-miles for SU trucks are according to figure 75. The 2012 miles for CU trucks are according to figure 76. Also shown in table 57 is the share of ton-miles in 2012.
Table 57. 2012 ton-miles, mile and share of ton-miles.
|
Result |
Calculation |
| Ton-miles SU, 2012 |
1.94 |
1.39*1.18*1.19 |
| Miles SU, 2012 |
0.40 |
1.39*0.29 |
| Ton- miles CU, 2012 |
12.70 |
1.199*1.011*10.48 |
| Miles CU, 2012 |
0.63 |
1.18*0.53 |
| SU Share of Ton-miles, 2012 |
14% |
1.94/(1.94+12.7) |
| CU Share of Ton-miles, 2012 |
86% |
12.7/(1.94+12.7) |
| SU Share of Miles, 2012 |
39.2% |
0.40/(0.40+0.63) |
| CU Share of Miles, 2012 |
60.8% |
0.63/(0.40+ 0.63) |
(Source: Federal Highway Administration.)
The payload factors for 2012 for SCTG 20 would be the 2012 Ton-miles divided by the 2012 Miles. This is figure 77 for SU truck and figure 78 for CU trucks. The Combined TPF for SU and CU trucks weighted by their respective share of ton miles, is according to figure 79. Those values are shown in table 58.
Table 58. Standard classification of transported goods 20 2012 truck payload factor for single unit, combination unit and combined combination unit and single unit trucks.
| Payload Factor |
Result |
Calculation |
| TPF SU,2012 |
4.92 |
1.199*4.10 |
| TPF CU,2012 |
19.99 |
1.011*19.77 |
| Combined CU and SU TPF,2012 |
14.08 |
0.392*1.199*4.10+0.608*1.011*19.77 |
(Source: Federal Highway Administration.)
