| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.1%
|
| -7 | Does not apply | 4 |
0.5%
|
| 0 | No obstacle | 619 |
74.5%
|
| 1 | Minor obstacle | 120 |
14.4%
|
| 2 | Moderate obstacle | 52 |
6.3%
|
| 3 | Major obstacle | 18 |
2.2%
|
| 4 | Very severe obstacle | 17 |
2%
|