| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.1%
|
| -7 | Does not apply | 4 |
0.3%
|
| 0 | No obstacle | 559 |
43%
|
| 1 | Minor obstacle | 402 |
30.9%
|
| 2 | Moderate obstacle | 244 |
18.8%
|
| 3 | Major obstacle | 74 |
5.7%
|
| 4 | Very severe obstacle | 16 |
1.2%
|