Transit Fare Arbitrage: Case Study of San Francisco Bay Area Rapid   Transit (BART) System
  Transit fare arbitrage is the scenario when two or more commuters agree to swap tickets during travel in such a way that total cost is lower than otherwise. Such arbitrage allows pricing inefficiencies to be explored and exploited, leading to improved pricing models. In this paper we discuss the basics of fare arbitrage through an intuitive pricing framework involving population density. We then analyze the San Francisco Bay Area Rapid Transit (BART) system to understand underlying inefficiencies. We also provide source code and comprehensive list of pairs of trips with significant arbitrage gain at github.com/asifhaque/transit-arbitrage. Finally, we point towards a uniform payment interface for different kinds of transit systems. 
Asif Haque
cs.CY