1. A method of verifying speed of a vehicle to provide independent verification of speed detected by a primary speed assessment system, said primary speed assessment system using a primary speed detector to detect speed of said vehicle, said method using a secondary speed assessment system independent of said primary speed detector, said method including: obtaining, using said secondary speed assessment system, first and second images of said vehicle, said second image being captured at a known time after said first image is captured; selecting a reference point on said vehicle in said first image; determining a location in said second image corresponding to an expected location of the selected reference point, based on the speed detected by the primary speed assessment system within a set percentage of the speed detected by the primary speed assessment system, in the time period between the capturing of said first and second images; and comparing an actual location of said reference point in said second image with the expected location, such that if the actual location corresponds to the expected location, it may be concluded that the vehicle was travelling at the speed detected by the primary speed assessment system.