Method and apparatus for determining the speed of a vehicle travelling along a road by processing images of the road

An apparatus for determining a speed of a vehicle travelling along a road by processing pairs of images of the road that have been captured by a camera mounted on the vehicle, each of the pairs of images having a common image coordinate system and comprising a first image of the road and a second image of the road, the first image having been captured at a first time instant, and the second image having been captured at a second time instant that is a predefined time period after the first time instant, wherein the first image and the second image comprise respective road marker images of a road marker on the road, the apparatus comprising:

• a location determination module arranged to determine a location, in the image coordinate system, of the road marker image in the first image;
• a location prediction module arranged to predict a location, in the image coordinate system, of an image of the road marker in the second image based on the determined location of the road marker image, an estimate of the speed of the vehicle, and the predefined time period;
• a road marker image detection module arranged to detect an image of the road marker in a portion of the second image at the predicted location;
• a distance estimation module arranged to estimate a distance by which the vehicle has travelled along the road during the predefined time period based on the determined location of the road marker in the first image, and a location of the detected image of the road marker in the portion of the second image;
• and
• a speed calculation module arranged to calculate the speed of the vehicle based on the estimated distance and the predefined time period.