Tire tracks
     Tires have several characteristics that make them important.  They could have class characteristics, like tread pattern, that can identify the brand or type of tire.  Individual characteristics make help to identify a specific tire on a specific vehicle.  Tread is the design on the tire.  The overall tread is placed by the tire manufacturer but driving patterns and conditions lead to small nicks or scuffs in the tread.  Rocks or other materials can get stuck in the tread and add to the pattern.  There are lots of helpful variables.

    Tires can tell the direction the vehicle is traveling, including changes in direction.  Police can tell if the vehicle backed up or was moving forward.  The front and rear width patterns are often different and distinguishable.  Track width is useful in determining the type of vehicle.  Width is the distance in inches between the middle of the same set of tires, either front or back.  Tread width is often different on vehicles because most people put different kinds of tires on front and back, often based on the type of wheel drive (front wheel or all wheel for example).  The marks then help determine the specific vehicle within that style.