| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 27 |
0.1%
|
| -7 | Does not apply | 37 |
0.2%
|
| 0 | No obstacle | 8080 |
43.3%
|
| 1 | Minor obstacle | 4763 |
25.5%
|
| 2 | Moderate obstacle | 3401 |
18.2%
|
| 3 | Major obstacle | 1806 |
9.7%
|
| 4 | Very severe obstacle | 543 |
2.9%
|