The last two decades have borne witness to considerable growth in the availabilityof interactive and 3D cartographies. However, questions about their true usefulness andusability remain, with the results of associated research drawing conflicting conclusions.This knowledge deficit is especially apparent within the design of cycling maps and cycleroute-planners. 3D cartography has enabled new forms of terrain visualisation for these usescenarios, but their usability relative to traditional methods of terrain visualisation is not yetfully understood. In response to this deficit, this thesis aimed to assess the relative usability(measured in terms of efficiency, effectiveness and user-preference) of 2D and 3D elevationvisualisations for cycle route-planners. ^In order to fulfil this aim, an empirical user-study was conducted with 36 participants.Participants were asked to solve a range of typical cycle route-planning tasks (related toheight detection, slope detection and climb estimation), for a variety of 2D (arrow, colour,elevation profile) and interactive 3D (3D elevation profile and 3D terrain model) elevationvisualisations. Study participants also provided feedback on their visualisation preference foreach of the tasks. These usability factors were assessed using a digital survey, which allowedinclusion of interactive 3D visualisations within a controlled experimental setting, whilst alsoautomatically logging user response times, user answers, and preference feedback. The findings demonstrated significant usability differences between individual2D and 3D elevation visualisations, although it was not possible to broadly state that onedimensionality was more or less `usable¿ than the other. ^Further, the usability of eachvisualisation was found to be strongly dependent upon the type of route-planning task.However, the 2D elevation profile was most efficient in the widest range of scenarios, andthose (generally 3D) visualisations which demanded interaction or high levels of cognitiveprocessing were least efficient. The results also showed that those visualisations which placedthe lowest cognitive load on the user were most effective; this factor appears to have had agreater influence on efficacy than the dimensionality of the visualisations. For all task types,users preferred 2D visualisations, most especially the 2D elevation profile.