| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 28 |
0.2%
|
| -7 | Does not apply | 20 |
0.1%
|
| 0 | No obstacle | 6757 |
36.2%
|
| 1 | Minor obstacle | 4270 |
22.9%
|
| 2 | Moderate obstacle | 4178 |
22.4%
|
| 3 | Major obstacle | 2589 |
13.9%
|
| 4 | Very severe obstacle | 815 |
4.4%
|