| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 2 |
0.1%
|
| -7 | Does not apply (spontaneous) | 3 |
0.2%
|
| 0 | No obstacle | 1268 |
80.6%
|
| 1 | Minor obstacle | 183 |
11.6%
|
| 2 | Moderate obstacle | 92 |
5.8%
|
| 3 | Major obstacle | 22 |
1.4%
|
| 4 | Very severe obstacle | 3 |
0.2%
|