| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 | 
                                                                 
                                    
                                    0.1%
                                 
                                                             | 
                                                        
                    
| -7 | Does not apply | 0 | 
                                                                 
                                    
                                    0%
                                 
                                                             | 
                                                        
                    
| 0 | No obstacle | 75 | 
                                                                 
                                    
                                    5.2%
                                 
                                                             | 
                                                        
                    
| 1 | Minor obstacle | 90 | 
                                                                 
                                    
                                    6.3%
                                 
                                                             | 
                                                        
                    
| 2 | Moderate obstacle | 192 | 
                                                                 
                                    
                                    13.4%
                                 
                                                             | 
                                                        
                    
| 3 | Major obstacle | 389 | 
                                                                 
                                    
                                    27.2%
                                 
                                                             | 
                                                        
                    
| 4 | Very severe obstacle | 685 | 
                                                                 
                                    
                                    47.8%
                                 
                                                             |