Scheme F99 is the decision trees described in Truck Characteristics Analysis, FHWA July 1999 with all redundancy removed. Note motorcycles have been restored.
| Class | Type | Axles | SP1 | SP2 | SP3 | SP4 | SP5 | Aggregate |
|---|
| 1 | F1 | 2 | 0.00-6.00 | | | | | 1 (Light) |
| 2 | F2 | 2 | 0.00-9.90 | | | | |
| 3 | F3 | 2 | | | | | |
| 3 | | | | | |
| 4 | 11.40-50.00 | | | | |
| 4 | | 0.00-22.00 | | | |
| 4 | F4 | 3 | | 0.00-5.80 | | | | 2 (Medium) |
| 5 | F5 | 2 | 12.10-50.00 | | | | |
| 5 | | 9.90-31.70 | | | |
| 6 | F6 | 3 | 0.00-18.80 | 0.00-5.80 | | | |
| 5 | | | | 0.00-3.50 | |
| 8 | F8 | 3 | | 20.90-50.00 | | | | 3 (Heavy) |
| 4 | | 24.70-50.00 | | | |
| 4 | | | 12.60-50.00 | | |
| 4 | | | | | |
| 9 | F9 | 5 | | 9.90-50.00 | | | |
| 5 | | | | | |
| 10 | F10 | 6 | | | | | 0.00-12.70 |
| 11 | F11 | 5 | | 9.90-40.00 | | 11.80-50.00 | |
| 12 | F12 | 6 | | | | | |
| 13 | F13 | 7-20 | | | | | |