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What we can learn from five naturalistic field experiments that failed to shift commuter behaviour
Ariella S Kristal1, Ashley V Whillans2
1Organizational Behavior Unit, Harvard Business School, Boston, MA, USA. akristal@hbs.edu.
Nature Human Behaviour
|December 25, 2019
Summary
Standard behavioral interventions, or nudges, failed to reduce single-occupancy vehicle commutes in five large field experiments. These findings underscore the challenges in changing commuter behavior and the need for publishing null results in sustainable travel research.
Area of Science:
- Behavioral Science
- Environmental Psychology
- Transportation Studies
Background:
- Commuting behavior significantly contributes to environmental impact.
- Behavioral interventions (nudges) are widely used to encourage sustainable transportation.
- Evidence on the effectiveness of nudges in reducing single-occupancy vehicle (SOV) commutes is mixed.
Purpose of the Study:
- To evaluate the effectiveness of standard behavioral interventions (nudges) in reducing SOV commutes.
- To assess the impact of carpooling nudges, non-cash incentives, and personalized travel plans on commuting behavior.
- To contribute to the cumulative knowledge on promoting sustainable travel by publishing null results.
Main Methods:
- Five large-scale field experiments involving 68,915 employees.
- Interventions included letters/emails promoting carpooling, non-cash incentives, and personalized travel plans.
- Statistical analysis included effect size calculations (Cohen's d) and equivalence testing.
Main Results:
- Carpooling nudges (Studies 1-2) did not increase carpool sign-up or usage.
- Non-cash incentives and personalized travel plans (Studies 3a-4) also showed no positive effect.
- Effect sizes ranged from -0.01 to 0.05, with four out of five experiments statistically equivalent to zero.
Conclusions:
- Standard behavioral interventions are largely ineffective in reducing SOV commutes.
- Changing commuter behavior requires more than simple nudges; significant barriers likely exist.
- Publishing null findings is crucial for advancing research on sustainable transportation and intervention design.