| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 4 |
0.2%
|
| -7 | Does not apply | 15 |
0.6%
|
| 0 | No obstacle | 416 |
15.8%
|
| 1 | Minor obstacle | 344 |
13.1%
|
| 2 | Moderate obstacle | 465 |
17.6%
|
| 3 | Major obstacle | 756 |
28.7%
|
| 4 | Very severe obstacle | 635 |
24.1%
|