| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.1%
|
| -7 | Does not apply | 4 |
0.4%
|
| 0 | No obstacle | 541 |
52.8%
|
| 1 | Minor obstacle | 268 |
26.1%
|
| 2 | Moderate obstacle | 159 |
15.5%
|
| 3 | Major obstacle | 50 |
4.9%
|
| 4 | Very severe obstacle | 2 |
0.2%
|