| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.2%
|
| -7 | Does not apply | 1 |
0.2%
|
| 0 | No obstacle | 355 |
74.9%
|
| 1 | Minor obstacle | 64 |
13.5%
|
| 2 | Moderate obstacle | 36 |
7.6%
|
| 3 | Major obstacle | 7 |
1.5%
|
| 4 | Very severe obstacle | 10 |
2.1%
|