| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 2 |
0.2%
|
| -7 | Does not apply | 5 |
0.5%
|
| 0 | No obstacle | 318 |
32.2%
|
| 1 | Minor obstacle | 235 |
23.8%
|
| 2 | Moderate obstacle | 290 |
29.4%
|
| 3 | Major obstacle | 92 |
9.3%
|
| 4 | Very severe obstacle | 45 |
4.6%
|