| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 3 |
0.4%
|
| -7 | Does not apply | 1 |
0.1%
|
| 0 | No obstacle | 120 |
15.8%
|
| 1 | Minor obstacle | 211 |
27.8%
|
| 2 | Moderate obstacle | 321 |
42.2%
|
| 3 | Major obstacle | 88 |
11.6%
|
| 4 | Very severe obstacle | 16 |
2.1%
|