| Value | Category | Cases | |
|---|---|---|---|
| 1 | Tar / tarmac (paved) | 8 |
5.5%
|
| 2 | Gravel | 52 |
35.6%
|
| 3 | Dust | 85 |
58.2%
|
| 96 | Other (specify) | 1 |
0.7%
|
| Sysmiss | 3 |