| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.2%
|
| -7 | Does not apply | 1 |
0.2%
|
| 0 | No obstacle | 169 |
28.1%
|
| 1 | Minor obstacle | 241 |
40.1%
|
| 2 | Moderate obstacle | 121 |
20.1%
|
| 3 | Major obstacle | 51 |
8.5%
|
| 4 | Very severe obstacle | 17 |
2.8%
|