MEXICAN NUMBER PLATES

Each Mexican state issues license plates of a different design. Most states change designs more or less every third year, with each state on its own plate replacement cycle. Every year Mexicans pay the "tenencia" or "revalidación de placas" (car plates renewal tax). A set of Mexican plates includes one pair of plates, a windshield sticker, and in a few states a plate sticker. In 2001 the size of the plate number was reduced in order to accommodate the addition of the state number, legend indicating the position of the number plate on the vehicle ("delantera" (front) or "trasera" (rear)), and additional graphics. European-sized plates do exist in Mexico, but are not official or technically even legal[3]. These generally contain the same design as the standard-size plate in use at the time, and bear the standard letter and number sequence.

Mexican number plates come in several different classification: Private, Private Fronteriza, Public, Public Frontera, Servicio Publico Federal, Inspeccion Fiscal y Aduanera, Armada de Mexico, and Secretaria de Relaciones Exteriores. The Fronteriza plates were introduced in 1972 and are available in the Mexico-USA border zone. This zone is formed by the Baja California and Baja California Sur states, as well as parts of Sonora, Chihuahua, Coahuila, and Tamaulipas. While the state of Nuevo León shares a 15 km border with the U.S., it does not have any cities within the border zone.
In the USA, ANPR systems are more commonly referred to as LPR (License Plate Reader or License Plate Recognition) technology or ALPR (Automatic License Plate Reader/Recognition) technology.

One of the biggest challenges with ALPR technology in the US is the accuracy of the Optical Character Recognition (OCR)—the actual identification of the characters on the license plate. Many variables affect OCR accuracy, starting with the fact that each state has multiple license plate designs that must be recognized by the ALPR system. Also, the shape of the characters, color of the plates and whether the characters are raised or flat can affect accuracy. Many times the letter D is mistaken for a Q or an O and some colors, especially reddish tones, are hard to read and as a result many system vendors will quote accuracy rates that are misleading. So potential buyers must be wary of any quoted % rates and ask what they mean as you will find that 90% really means 90% (N-1 or N-2). This little detail in the brackets (which will not be either obvious or explained up front) allows the vendor to get all chracters in a plate correct except one (N-1) or two (N-2).