| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.1%
|
| -7 | Does not apply | 1 |
0.1%
|
| 0 | No obstacle | 43 |
3.3%
|
| 1 | Minor obstacle | 53 |
4%
|
| 2 | Moderate obstacle | 215 |
16.3%
|
| 3 | Major obstacle | 663 |
50.2%
|
| 4 | Very severe obstacle | 346 |
26.2%
|