| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.1%
|
| -7 | Does not apply | 1 |
0.1%
|
| 0 | No obstacle | 533 |
54.4%
|
| 1 | Minor obstacle | 256 |
26.1%
|
| 2 | Moderate obstacle | 132 |
13.5%
|
| 3 | Major obstacle | 54 |
5.5%
|
| 4 | Very severe obstacle | 2 |
0.2%
|