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Accessibility maps can be used in a number of ways as aids to development decision making.
As in all spatial modelling, the quality and accuracy of both inputs and outputs must be always be borne in mind. These physical attributes are further qualified by the subjective content of the model, such as speed of travel, impact of slope, permeability of barriers and so on. Accessibility maps can only be indicative at best, and will not give accurate numeric results However, in rural locations with relatively restricted transportation systems, they can give a very good indication of areas of temporal remoteness which can inform development decision making processes.
A further important limitation of the model comes from the edge effect of the map. Any targets outside of the model area will have no influence on the model at all, but may be very important targets in reality. In the examples shown, the northern areas generally have the worst accessibility. However, if there was a school just north of the border of the map, this could mean that service provision in this areas was in reality quite good (figure 16). Edge effects should be minimised by taking the model right up to real natural boundaries, such as the sea coast or possibly national borders, or well beyond the extent of the study area, so that it is not unduly influenced by the map edge effect. Values anywhere near the edges must be treated with caution and tested against local knowledge of the area.