| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.1%
|
| -7 | Does not apply | 27 |
2.8%
|
| 0 | No obstacle | 408 |
42.2%
|
| 1 | Minor obstacle | 283 |
29.3%
|
| 2 | Moderate obstacle | 177 |
18.3%
|
| 3 | Major obstacle | 54 |
5.6%
|
| 4 | Very severe obstacle | 16 |
1.7%
|