| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.1%
|
| -7 | Does not apply | 8 |
0.8%
|
| 0 | No obstacle | 113 |
11.9%
|
| 1 | Minor obstacle | 159 |
16.8%
|
| 2 | Moderate obstacle | 277 |
29.3%
|
| 3 | Major obstacle | 267 |
28.2%
|
| 4 | Very severe obstacle | 122 |
12.9%
|