A controller receives images from a rearward-facing camera having an inter-lane region in the field of view thereof. A region of interest of the images is identified corresponding to the inter-lane region. The region of interest is converted to a grayscale image having a drastically reduced number of intensity levels. A difference image is determined between the grayscale image for each image relative to the grayscale image of a preceding image. If the non-zero pixels in the difference image exceed a threshold and the area of non-zero pixels in the difference images for the input images are increasing with time, a lane-splitting vehicle will be determined to be present and an alert may be generated and/or autonomous lane changes may be suppressed.