| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.1%
|
| -7 | Does not apply | 2 |
0.2%
|
| 0 | No obstacle | 586 |
57.2%
|
| 1 | Minor obstacle | 255 |
24.9%
|
| 2 | Moderate obstacle | 107 |
10.4%
|
| 3 | Major obstacle | 66 |
6.4%
|
| 4 | Very severe obstacle | 7 |
0.7%
|