| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 10 |
0.1%
|
| -7 | Does not apply | 23 |
0.1%
|
| 0 | No obstacle | 7094 |
38%
|
| 1 | Minor obstacle | 4786 |
25.7%
|
| 2 | Moderate obstacle | 3386 |
18.1%
|
| 3 | Major obstacle | 2403 |
12.9%
|
| 4 | Very severe obstacle | 955 |
5.1%
|