| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 5 |
0.5%
|
| -7 | Does not apply | 1 |
0.1%
|
| 0 | No obstacle | 666 |
66.9%
|
| 1 | Minor obstacle | 172 |
17.3%
|
| 2 | Moderate obstacle | 92 |
9.2%
|
| 3 | Major obstacle | 46 |
4.6%
|
| 4 | Very severe obstacle | 13 |
1.3%
|