| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.2%
|
| -7 | Does not apply | 1 |
0.2%
|
| 0 | No obstacle | 365 |
60.8%
|
| 1 | Minor obstacle | 128 |
21.3%
|
| 2 | Moderate obstacle | 81 |
13.5%
|
| 3 | Major obstacle | 21 |
3.5%
|
| 4 | Very severe obstacle | 3 |
0.5%
|