| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.1%
|
| -7 | Does not apply | 5 |
0.4%
|
| 0 | No obstacle | 435 |
36.3%
|
| 1 | Minor obstacle | 196 |
16.3%
|
| 2 | Moderate obstacle | 243 |
20.3%
|
| 3 | Major obstacle | 207 |
17.3%
|
| 4 | Very severe obstacle | 113 |
9.4%
|