| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 3 |
0.5%
|
| -7 | Does not apply | 5 |
0.8%
|
| 0 | No obstacle | 29 |
4.5%
|
| 1 | Minor obstacle | 50 |
7.8%
|
| 2 | Moderate obstacle | 183 |
28.4%
|
| 3 | Major obstacle | 250 |
38.8%
|
| 4 | Very severe obstacle | 125 |
19.4%
|