1. A method for determining the speed of a motor vehicle in a vehicle speed detection system, the method comprising: receiving a plurality of infrared images of a motor vehicle traveling on a road, each of said images being separated in time by a known interval, said infrared images having been captured using an infrared imaging system operating in an infrared wavelength band selected such that a contrast between the tires of said vehicle and the road surface is enhanced in said images; determining, for each of at least two of said images, a point of contact where a same tire of said vehicle contacts said road surface, such that a height of each point of contact is zero; mapping said points of contact to a (x,y) two dimensional coordinate system, such that each point of contact has a (x,y) set of coordinates; using said coordinates and said time interval separations to calculate a speed at which said vehicle is traveling on said road; and communicating said vehicle's speed to a computer system.