From When nudges aren’t enough: Norms, incentives and habit formation in public transport usage by Christina Gravert and Linus Olsson Collentine. From the Abstract:
In a large-scale natural experiment with over 14,000 individuals, we investigate whether public transport usage can be influenced by social norms and by economic incentives. Despite their effectiveness in other domains, we find a tightly estimated zero for descriptive social norms on ridership. Increasing the economic incentive, by doubling the trial period, significantly increases uptake and long-term usage. This increase is sustained for months after removing the incentive. The effect is mainly driven by initial low users, which is evidence for habit formation and highlights the heterogeneous effects of the policy. While there is scope for long-term behavior change, norm nudges might not be the most promising approach.
This is the Achille's Heel of public transport. Enthusiasts treat it as a matter of knowledge and habit. To a minimal degree, that is true.
At its heart, though, public transport usage is a trade-off decision anchored on an individual's time value. In many/most cities in the US, public transportation is infrequent, inconvenient and slow. A journey which is thirty minutes by car can be 60-90 minutes by public transportation.
I am confident that there is some monetary inflection point between car and public transportation but I have never seen a study which would reveal what it is. If you earn minimum wage, then you eat the extra time it takes. But if you earn a hundred dollars an hour, there is a conscious or unconscious mental calculation: Is it worth taking public transportation given that an extra hour of reduced travel time is worth $100 to me.
Contra Gravert and Collentine, the issue is not about awareness and knowledge. They want it to be about knowledge and awareness but their study seems more supportive of the time values perspective.
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