The "Smartcard Plus" experiment involves travellers adding money to their smartcards which is automatically debited as they travel, like on the Glasgow Subway and similar to London's Oyster card for buses and tubes.
It has been launched on the Cathcart Circle, Newton and Neilston lines between Glasgow Central and 15 stations on the south side of the city.
Passengers tap their card on ticket gates or electronic readers at the start and end of their journeys which calculates the cheapest fare and deducts the cost.
Commuters have their travel costs capped at the level of a weekly season ticket.
Smartcards can also be set so credit is automatically kept topped up.
Elsewhere on the ScotRail network, smartcards can only currently be used by pre-loading individual tickets, such as singles, returns and season tickets.
ScotRail said the trial, launched in January, is due to continue until May.
A spokesman said: "Once the trial has concluded, we will be in a better position to understand if/when/where this scheme will be expanded."
BACKGROUND: ScotRail passengers say no to smartcardsScotRail head of revenue development Claire Dickie said: “We are delighted to be involved in this innovative trial.
"Customers are changing the way they want to do business with us and we see account-based ticketing as one of the potential ways to improve the overall customer experience.”
Cubic Transportation Systems, which is running the trial with ScotRail, said it could be extended to cover other types of travel.
Laurent Eskenazi, its Europe managing director, said: “Cubic’s One Account delivers an end-to-end multi-modal platform that can be extended to the UK’s entire public transport network.”