“…In Proof-of-Payment Transit Systems (POP-TSs), passengers have to buy tickets before boarding vehicles; however, they are not automatically checked and may opportunistically decide to evade the fare. Many strategies can be adopted by TAs/PTCs to face fare evasion, the most relevant being passenger inspections and fine charging (Multisystems et al, 2002;Sasaki, 2014;Guarda et al, 2016;Dai et al, 2017;Alhassan et al, 2022;Wolfgram et al, 2022).…”