| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.1%
|
| -7 | Does not apply | 1 |
0.1%
|
| 0 | No obstacle | 228 |
22.6%
|
| 1 | Minor obstacle | 223 |
22.1%
|
| 2 | Moderate obstacle | 280 |
27.8%
|
| 3 | Major obstacle | 160 |
15.9%
|
| 4 | Very severe obstacle | 114 |
11.3%
|