| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 7 | 
                                    
                                    1.9%
                                 | 
| -7 | Does not apply | 18 | 
                                    
                                    5%
                                 | 
| 0 | No obstacle | 207 | 
                                    
                                    57%
                                 | 
| 1 | Minor obstacle | 37 | 
                                    
                                    10.2%
                                 | 
| 2 | Moderate obstacle | 40 | 
                                    
                                    11%
                                 | 
| 3 | Major obstacle | 40 | 
                                    
                                    11%
                                 | 
| 4 | Very severe obstacle | 14 | 
                                    
                                    3.9%
                                 |