A good read on the history of CEPAS up to 2015
here.
It was noted that the response rate of CEPAS is 180ms within a range of 8 cm.
A
recent article on a writer in favour of closed systems (stored value cards) noted that transit-oriented cards like CEPAS were originally intended for quick clearance of commuters at the gates, and that we are turning the clock backwards by allowing EMVCo transactions with response times two-thirds slower (500ms) at the gate. No doubt it is convenient, but that convenience will probably only be realised if foreign-issued cards were allowed (which is difficult to implement due to trust issues).
The writer suggests that local transit card issuers work towards emulating transit cards on phones and allowing foreign cards to be used to top up these digital transit cards (e.g., Apple's Express Transit option used in Japan's SuiCa, Beijing and Shanghai). This could reinstate the faster response rates associated with high-volume transit transactions and allow top-ups/recharges to be done offline via a trusted mechanism (Apple Pay wallet).
But I do understand that the CEPAS standard is difficult to emulate owing to the partial refund feature needed for distance fares (instead of deducting only upon exit), though I think if this can be emulated, it would technically allow cities which use distance based charging like Seoul to hop on.