lane1                                                                                                                        lane2           
                                                                                                                                                                                 
                                                                                                                                                                                 
                                                                                                                                                                                 
                                                                                                                                                                                 
                                              no                                                                                                                                 
                                                                                condition                                                                                        
                                                                                                                                                                                 
                                                                                                                                   yes                                           
                                                                                                                                                                                 
                                                                                                                                                                                 
                                                                                                                                                                     do something