SEPTA is taking the next step in its introduction of its smart fare card, SEPTA Key, to Regional Rail.

On Oct. 1, riders who board in SEPTA's Zone Three and have weekly or monthly fare plans will have the option of transferring those plans to a SEPTA Key card. With 50 stations used by 25,000 riders, Zone Three is the largest of the four Regional Rail Zones. Key was introduced to Zone Four in August.

SEPTA hopes to introduce Key to the remaining two zones by the end of the year. It may be introduced to both at once, officials said.

Key cards loaded with the monthly fare option will be available for sale starting Sept. 20, and cards with the weekly fare option are available Sept. 26. People who already have a Key card can load one of the fare options onto those.

SEPTA has spent close to $200 million to create a single-fare system across all its services. The Key has displaced tokens on city transit and eventually will replace the current paper tickets and passes used by Regional Rail riders. For now, though, using Key to pay for Regional Rail trips is optional. Other fare systems will continue to be in effect, and for now, employer-managed commuter programs aren't usable on SEPTA Key.