This paper describes a new approach to image enhancement for people with severe visual impairments to enable mobility in an urban environment. A neural-network classifier is used to identify objects in a scene so that image content specifically important for mobility may be made more visible. Enhanced images are displayed to the user using a high saturation colour scheme where each type of object has a different colour, resulting in images which are highly visible and easy to interpret. The object classifier achieves a level of accuracy over 90%. Results from a pilot study conducted using people with a range of visual impairments are presented in which performance on a difficult mobility-related task was improved by over 100% using the system.