| Value | Category | 
                                    
                    
                        | 00 | NIU (not in universe) | 
                                    
                    
                        | 10 | None, does not travel to work or school | 
                                    
                    
                        | 20 | Walking | 
                                    
                    
                        | 21 | Walks or bicycle | 
                                    
                    
                        | 22 | Walks, bicycle, or motorcycle | 
                                    
                    
                        | 30 | Private vehicle | 
                                    
                    
                        | 31 | Auto, truck, van | 
                                    
                    
                        | 32 | Auto (driver) | 
                                    
                    
                        | 33 | Auto (passenger) | 
                                    
                    
                        | 34 | Auto, motorcycle, moped | 
                                    
                    
                        | 35 | Motorcycle, moped, or scooter | 
                                    
                    
                        | 36 | Bicycle | 
                                    
                    
                        | 37 | Bicycle or motorcycle/moped | 
                                    
                    
                        | 38 | Boat | 
                                    
                    
                        | 40 | Public transportation | 
                                    
                    
                        | 41 | Bus or trolley bus | 
                                    
                    
                        | 42 | Bus or streetcar | 
                                    
                    
                        | 43 | Streetcar or trolley car | 
                                    
                    
                        | 44 | Railroad or train | 
                                    
                    
                        | 45 | Subway or elevated train | 
                                    
                    
                        | 46 | Other public transportation | 
                                    
                    
                        | 50 | Other | 
                                    
                    
                        | 51 | Taxicab | 
                                    
                    
                        | 52 | Ferryboat | 
                                    
                    
                        | 53 | Special transportation (company coach, school bus, etc.) | 
                                    
                    
                        | 54 | Hired transport | 
                                    
                    
                        | 55 | Shared private transport | 
                                    
                    
                        | 56 | Horse or animal-drawn vehicle | 
                                    
                    
                        | 57 | Other, not elsewhere classified | 
                                    
                    
                        | 60 | Combination of several means | 
                                    
                    
                        | 99 | Unknown/missing | 
                            
            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.