SEPTA is contending with a new kind of fare evasion, in which enterprising scammers are using Key cards to give cash-paying riders a discounted trip on the Broad Street Line and the El. Because SEPTA does not track or estimate revenue losses due to fare evasion, said Rich Burnfield, deputy general manager and treasurer, the agency can’t say whether more people are dodging fares than usual. Cashiers working on the subway lines, however, insist scofflaws are proliferating. […] The latest trend is made possible by the Key card, which offers a $2-per-ride fare, compared with $2.50 for customers paying cash...