| Value | Category | 
                                    
                    
                        | 1 | Road | 
                                    
                    
                        | 2 | Rail | 
                                    
                    
                        | 3 | Air | 
                                    
                    
                        | 4 | Sea | 
                                    
                    
                        | 5 | Lake | 
                                    
                    
                        | 6 | Not applicable | 
                                    
                    
                        | 99 | No other alternative | 
                                    
                    
                        | Sysmiss |  | 
                            
            Warning: these figures indicate the number of cases found in the data file. They cannot be interpreted as summary statistics of the population of interest.