By Mike DeNardo

PHILADELPHIA (CBS) -- SEPTA plans to introduce a stored-value feature and senior cards to its "SEPTA Key" fare program by the end of the year.

You can buy the re-loadable, tap-and-go SEPTA Key cards at an increasing number of locations. But right now, their function is limited.

Riders can only load the value of a weekly or monthly TransPass on them. SEPTA Deputy General Manager, Rich Burnfield says in November the transit agency expects to roll out a stored-value feature for occasional riders.

"A Travel Wallet is where a customer could add value to a card, say, $5, $10, $20 and then use that card on a per-trip basis. And SEPTA expects to launch that towards the end of this calendar year -- looking to launch sometime in mid-to-late November."

Next month, SEPTA begins mailing 40,000 photo-embedded senior fare cards for early adopters. But Burnfield says seniors will still be able to ride transit free without them.

He says a full roll-out of the electronic fare collection system isn't expected until sometime in 2017, and there will be a transition period during which tokens and TransPasses will still be accepted.

Burnfield says SEPTA is also developing a SEPTA Key mobile app, to allow commuters to pay for rides using their cell phones.