| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 33 |
0.2%
|
| -7 | Does not apply | 54 |
0.3%
|
| 0 | No obstacle | 8392 |
45%
|
| 1 | Minor obstacle | 4225 |
22.6%
|
| 2 | Moderate obstacle | 2824 |
15.1%
|
| 3 | Major obstacle | 2004 |
10.7%
|
| 4 | Very severe obstacle | 1125 |
6%
|