1. A method for determining a region of interest in an image, this method being implemented in a road vehicle, said method comprising the following steps: a plurality of lines L i i=1,. .. , n formed by pixels is defined in the image; in each line L i , a plurality of segments S j j=1,. .. , m constituted by pixels is defined; a luminance level NVG(S j ) is calculated for each segment S j based on the luminance of the pixels constituting this segment S j ; depending on this luminance level NVG(Sj), the segment S j is selected or excluded from the region of interest; and the region of interest is obtained by amalgamating all the segments selected for each line; wherein the segment S j is excluded from the region of interest if the length of this segment S j is less than a predetermined minimum length.