| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.1%
|
| -7 | Does not apply | 15 |
1%
|
| 0 | No obstacle | 1220 |
77.6%
|
| 1 | Minor obstacle | 188 |
12%
|
| 2 | Moderate obstacle | 97 |
6.2%
|
| 3 | Major obstacle | 37 |
2.4%
|
| 4 | Very severe obstacle | 15 |
1%
|