Editing MetroCard (section)

==Technology==
[[File:nyc transit authority token.png|thumb|150px|right|A NYCTA token]]
During a swipe, the MetroCard is read, re-written to, then check-read to verify correct encoding.<ref>Riazi, Atefeh. MetroCard: Automating New York City's Public Transit System. Proceedings of the First International Conference on Urban Transportation Systems, American Society of Civil Engineers, Miami, Fla. (March 21–25, 1999).</ref>

[[File:Select Bus Service bus shelter.jpg|thumb|left|250px|[[Select Bus Service]] pay shelter for pre-payment of fare before boarding [[Select Bus Service]] buses.]]
Each MetroCard [[stored value card]] is assigned a unique, permanent ten-digit [[serial number]] when it is manufactured. The value is stored [[Digital card#Magnetic storage|magnetically]] on the card itself, while the card's transaction history is held centrally in the Automated Fare Collection (AFC) [[Database]]. When a card is purchased and fares are loaded onto it, the MetroCard Vending Machine or station agent's computer stores the amount of the purchase onto the card and updates the database, identifying the card by its serial number. Whenever the card is swiped at a turnstile, the value of the card is read, the new value is written, the customer is let through, and then the central database is updated with the new transaction as soon as possible. Cards are not validated in real time against the database when swiped to pay the fare.<ref name=":7">{{Cite web|last=McClain|first=Noah|date=July 15, 2019|title=Caught inside the black box: Criminalization, opaque technology, and the New York subway MetroCard|url=https://www.researchgate.net/publication/334683186|archive-url=|archive-date=|access-date=December 22, 2020|website=Researchgate}}</ref> The AFC Database is necessary to maintain transaction records to track a card if needed. It has actually been used to acquit criminal suspects<ref>{{cite news |title=Murder Case Dropped After MetroCard Verifies Alibi |first=Benjamin |last=Weiser |url=https://www.nytimes.com/2009/01/01/nyregion/01murder.html |newspaper=The New York Times |date=December 31, 2008 |access-date=April 25, 2010}}</ref> by [[Alibi|placing them away]] from the [[crime scene|scene of a crime]]. The database also stores a list of MetroCards that have been invalidated for various reasons. Reasons include the MetroCard being lost, stolen, expired student, or an expired monthly card, and it distributes the list to turnstiles in order to deny access to a revoked card.

The older blue MetroCards were not capable of the many kinds of fare options that the gold ones currently offer. The format of the [[magnetic stripe]] used by the blue MetroCard offered very little other than the standard pay-per-swipe fare. Gold MetroCards allow groups of people (up to four) to ride together using a single pay-per-swipe MetroCard. The gold MetroCard keeps track of the number of swipes at a location in order to allow those same number of people to transfer at a subsequent location, if applicable. The MetroCard system was designed to ensure [[backward compatibility]], which allowed a smooth transition from the blue format to gold.<ref>{{cite news |last=Pierre-Pierre |first=Garry |date=February 21, 1997 |title=205 More Buses Ordered To Handle Free Transfers |url=https://query.nytimes.com/gst/abstract.html?res=F10A17FA3E5A0C728EDDAB0894DF494D81 |access-date=April 25, 2010 |newspaper=The New York Times}}</ref>

Cubic later used the proprietary MetroCard platform to create the [[Chicago Card]] and [[Tren Urbano]]'s fare card, which are physically identical to the MetroCard except for the labeling.