1. A vehicle-based lane tracking device including a processing system configured to receive optical images of a roadway adjacent the vehicle, to process said images and to output vehicle control signals in response thereto, said system operative to perform process steps, comprising: modeling the lane marker by the system, in the range of a minimum predetermined lane marker width to a maximum predetermined lane marker width; splitting the lane marker model into a left step and a right step by the system, wherein the right step has a negative value of a left step value; calculating a cumulative sum (S k ) from the lane marker model by the system, wherein k is a kth pixel; calculating a filter response from the cumulative sum by the system; and normalizing the filter response by the system comprising compensating for at least one of filter pixel scale size and illumination, wherein compensating for illumination comprises normalizing for illumination by apparent brightness of the lane marker and apparent brightness of a road on which the lane marker is located, wherein normalizing for the brightness of the lane marker comprises dividing the normalized filter response by a bright section measurement of the filter response to obtain an illumination normalized response (Z k ) by the system, and further comprising detecting a threshold peak from the lane marker model by the system to find an edge of the lane marker, wherein the threshold peak is at least one of a positive peak and a negative peak, wherein the threshold peak is detected when |Z k |>τ 1 ( f bright k ) and f bright k >τ 2 ( w k ), wherein f bright k =max( f right k , f left k ), wherein τ 1 (f bright k ) and τ 2 (w k ) are set to predetermined values, and wherein w k is an observed road brightness, and wherein the threshold peak is further defined by a five-point neighborhood centered about a current point requiring 
 Z k−2 <Z k and Z k−1 ≦Z k and Z k+1 ≦Z k and Z k+2 <Z k when z > 0, and Z k−2 >Z k and Z k−2 ≧Z k and Z k+1 ≧Z k and Z k+2 >Z k when Z< 0.