| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 5 |
0.5%
|
| -7 | Does not apply | 10 |
1%
|
| 0 | No obstacle | 560 |
57.2%
|
| 1 | Minor obstacle | 260 |
26.6%
|
| 2 | Moderate obstacle | 114 |
11.6%
|
| 3 | Major obstacle | 28 |
2.9%
|
| 4 | Very severe obstacle | 2 |
0.2%
|