A method of determining the characteristics of a scene around a vehicle, comprising: capturing a stereo pair of images of the scene, processing the images to produce a depth map of the scene in which each pixel in the depth map is assigned a value that corresponds to the range of a corresponding region in the scene, the pixels arranged in a grid of rows and columns with each column of pixels in the grid corresponding to a vertically oriented set of regions in the scene and each row a horizontally oriented set of regions in the scene, Binning the values for one or more columns of pixels in the depth map to form a corresponding histogram, each bin in the histogram having a count value that corresponds to the number of pixels in the column that have a depth within the range assigned to the bin, representing the set of histograms as a histogram image, with each histogram defining the values of one column in the histogram image, providing a normalization image of the same dimensions as the histogram image by fitting a function to a range-bin count of a known flat plane observed in the acquired data, subtracting the normalization image from the histogram image to produce a set of normalized range bin histograms, processing each of the normalized range bin histograms to determine for each histogram the lowest range bin that is indicative that an object that represents a non-drivable region is present at a depth that lies in the range of depths assigned to the bin and thereby identify the location of one or more boundary points that lie on a boundary of a drivable space in the scene. in which the step of processing each range bin histogram to determine which is the lowest range bin that is indicative that an object that represents a non-drivable region is present at a depth that lies in the range of depths assigned to the bin comprises scanning along a column in the histogram starting with the lowest range bin until a bin corresponding to non-driveable space is found whereby the scanning is stopped once a boundary point is detected and the scanning moves to a next histogram; whereby the boundary points form a set that identifies a boundary line representing an edge of a safe drivable space in the scene. capturing a stereo pair of images of the scene, processing the images to produce a depth map of the scene in which each pixel in the depth map is assigned a value that corresponds to the range of a corresponding region in the scene, the pixels arranged in a grid of rows and columns with each column of pixels in the grid corresponding to a vertically oriented set of regions in the scene and each row a horizontally oriented set of regions in the scene, Binning the values for one or more columns of pixels in the depth map to form a corresponding histogram, each bin in the histogram having a count value that corresponds to the number of pixels in the column that have a depth within the range assigned to the bin, representing the set of histograms as a histogram image, with each histogram defining the values of one column in the histogram image, providing a normalization image of the same dimensions as the histogram image by fitting a function to a range-bin count of a known flat plane observed in the acquired data, subtracting the normalization image from the histogram image to produce a set of normalized range bin histograms, processing each of the normalized range bin histograms to determine for each histogram the lowest range bin that is indicative that an object that represents a non-drivable region is present at a depth that lies in the range of depths assigned to the bin and thereby identify the location of one or more boundary points that lie on a boundary of a drivable space in the scene. in which the step of processing each range bin histogram to determine which is the lowest range bin that is indicative that an object that represents a non-drivable region is present at a depth that lies in the range of depths assigned to the bin comprises scanning along a column in the histogram starting with the lowest range bin until a bin corresponding to non-driveable space is found whereby the scanning is stopped once a boundary point is detected and the scanning moves to a next histogram; whereby the boundary points form a set that identifies a boundary line representing an edge of a safe drivable space in the scene.