| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 2 |
0.2%
|
| -7 | Does not apply | 1 |
0.1%
|
| 0 | No obstacle | 173 |
17.5%
|
| 1 | Minor obstacle | 155 |
15.7%
|
| 2 | Moderate obstacle | 368 |
37.3%
|
| 3 | Major obstacle | 212 |
21.5%
|
| 4 | Very severe obstacle | 76 |
7.7%
|