Temporary incentives Change Daily Routines: Evidence from a Field Experiment on Singapore's Subways

We show that temporary incentives can lead to lasting changes in people's daily routines through a field experiment. In randomized controlled trials on Singapore's subways, commuters in the treatment group received a full rebate of their fares for 10 weeks if they exited fare gates before the start of morning peak-travel time. The objective of the fare promotion was to alleviate peak-time congestion by encouraging commuters to travel prepeak. This promotion resembles an actual public program implemented in Singapore in 2013. Using participants' fare cards, we obtained a rich data set for 60 weeks' worth of trips. A difference-in-differences analysis reveals that the effect of the free-trip offer was modest but robust during the promotional period: on average, trips were 5.5% more likely to end before the morning peak time. More encouragingly, the modest shift toward early travel strongly persisted even seven months after the end of the free-trip offer. This seemingly small shift could imply large financial savings on infrastructure investment. We find suggestive evidence that travel regularity and consistency during the promotion appear to be important for forging persistence.