| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.1%
|
| -7 | Does not apply | 5 |
0.5%
|
| 0 | No obstacle | 336 |
30.7%
|
| 1 | Minor obstacle | 225 |
20.5%
|
| 2 | Moderate obstacle | 188 |
17.2%
|
| 3 | Major obstacle | 240 |
21.9%
|
| 4 | Very severe obstacle | 101 |
9.2%
|