| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 11 |
0.1%
|
| -7 | Does not apply | 17 |
0.2%
|
| 0 | No obstacle | 4766 |
50.8%
|
| 1 | Minor obstacle | 2339 |
24.9%
|
| 2 | Moderate obstacle | 1273 |
13.6%
|
| 3 | Major obstacle | 710 |
7.6%
|
| 4 | Very severe obstacle | 260 |
2.8%
|