| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.1%
|
| -7 | Does not apply | 26 |
2.7%
|
| 0 | No obstacle | 400 |
42.2%
|
| 1 | Minor obstacle | 281 |
29.7%
|
| 2 | Moderate obstacle | 171 |
18.1%
|
| 3 | Major obstacle | 52 |
5.5%
|
| 4 | Very severe obstacle | 16 |
1.7%
|