| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.1%
|
| -7 | Does not apply | 4 |
0.3%
|
| 0 | No obstacle | 453 |
37.8%
|
| 1 | Minor obstacle | 204 |
17%
|
| 2 | Moderate obstacle | 211 |
17.6%
|
| 3 | Major obstacle | 204 |
17%
|
| 4 | Very severe obstacle | 123 |
10.3%
|