A navigation device comprising: a processing section; and an output section for providing an output responsive to the processing section; wherein the processing section has access to map data and avoidance data, the avoidance data including information for identifying undesirable locations, and the processing section is arranged to: receive location information representing a geographical location and direction of travel in relation to the map data; establish, based on the location information and map data, whether the geographical location and direction of travel approach a navigation decision point having a plurality of navigation choices, where each navigation choice corresponds to an onward route leaving the navigation decision point; determine, based on the map data and avoidance data, for at least one onward route leaving the navigation decision point, whether the onward route unavoidably includes an undesirable location; and provide result information to the output section based, at least in part, on the determination, wherein the navigation device is arranged to receive time data representative of at least one of a current time or an expected time at which an undesirable location will be reached, and wherein: the avoidance data is time-dependent, and the processing section is configured to perform the determination based, at least in part, on the time data, wherein the processing section is configured to investigate whether a degree to which an undesirable location is undesirable will change within a predetermined time period, and at least one of: the result of this investigation is used in the determination of whether the onward route unavoidably includes an undesirable location, and the result information provided to the output section includes the result of this investigation, characterised in that the result information includes a recommendation to wait in order to reduce the degree to which an undesirable location is undesirable. a processing section; and an output section for providing an output responsive to the processing section; wherein the processing section has access to map data and avoidance data, the avoidance data including information for identifying undesirable locations, and the processing section is arranged to: receive location information representing a geographical location and direction of travel in relation to the map data; establish, based on the location information and map data, whether the geographical location and direction of travel approach a navigation decision point having a plurality of navigation choices, where each navigation choice corresponds to an onward route leaving the navigation decision point; determine, based on the map data and avoidance data, for at least one onward route leaving the navigation decision point, whether the onward route unavoidably includes an undesirable location; and provide result information to the output section based, at least in part, on the determination, receive location information representing a geographical location and direction of travel in relation to the map data; establish, based on the location information and map data, whether the geographical location and direction of travel approach a navigation decision point having a plurality of navigation choices, where each navigation choice corresponds to an onward route leaving the navigation decision point; determine, based on the map data and avoidance data, for at least one onward route leaving the navigation decision point, whether the onward route unavoidably includes an undesirable location; and provide result information to the output section based, at least in part, on the determination, wherein the navigation device is arranged to receive time data representative of at least one of a current time or an expected time at which an undesirable location will be reached, and wherein: the avoidance data is time-dependent, and the processing section is configured to perform the determination based, at least in part, on the time data, the avoidance data is time-dependent, and the processing section is configured to perform the determination based, at least in part, on the time data, wherein the processing section is configured to investigate whether a degree to which an undesirable location is undesirable will change within a predetermined time period, and at least one of: the result of this investigation is used in the determination of whether the onward route unavoidably includes an undesirable location, and the result information provided to the output section includes the result of this investigation, the result of this investigation is used in the determination of whether the onward route unavoidably includes an undesirable location, and the result information provided to the output section includes the result of this investigation, characterised in that the result information includes a recommendation to wait in order to reduce the degree to which an undesirable location is undesirable.