Singapore's Land Transport Authority on Thursday doubled the cash incentives in a web-based study to encourage more commuters to put their journeys at off-peak hours.

The web-based study comprises a reward system where commuters can earn credits based on the start times of their trips at the train stations and the distance of their journeys.

The maximum cash prize for participants in the study has been doubled to 200 Singapore dollars (164 US dollars), and it can be transferred directly to the participants' bank accounts if they choose to. Previously, cash rewards were credited into their tap-to-pay transport cards.

The authority said that more than 320,000 Singapore dollars have been paid out since January. The number of participants in the study have more than doubled to 41,000.

It also made adjustments to the reward system so that more credits per kilometer are given to participants, depending on the number of off-peak trips they make.

Participants can get up to six credits per kilometer, compared with three credits per trip for all participants.

The Land Transport Authority said it hopes the study can eventually cover up to 60,000 commuters.