| Stability Class | Exponent (p) | |
| Rough Surface (urban) | Smooth Surface (rural) | |
| A | 0.15 | 0.07 |
| B | 0.15 | 0.07 |
| C | 0.20 | 0.10 |
| D | 0.25 | 0.15 |
| E | 0.30 | 0.35 |
| F | 0.30 | 0.35 |