A vehicle speed measurement method and system for identifying a violating vehicle utilizing single image capturing unit. A vehicle image can be captured by the image capturing unit in order to estimate speed of the vehicle utilizing an ALPR unit. The license plate characters can be located and extracted from the captured image. A distance of the license plate from the image capturing unit can be calculated utilizing a physical character height from a reference point of the image capturing unit and a pixel character height generated by the ALPR unit. A position of the license plate in the field of view of the image capturing unit along with the distance information can be utilized to determine a height of the license plate from a road surface. The height of the license plate can be employed to accurately estimate the vehicle speed.