| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 5 |
0.5%
|
| -7 | Does not apply | 1 |
0.1%
|
| 0 | No obstacle | 459 |
41.9%
|
| 1 | Minor obstacle | 178 |
16.2%
|
| 2 | Moderate obstacle | 163 |
14.9%
|
| 3 | Major obstacle | 231 |
21.1%
|
| 4 | Very severe obstacle | 59 |
5.4%
|