A Portland bike-sharing flyer reached new movers during their „window of openness“—quadrupling sign-ups from 0.31% to 1.14%
What unsustainable behaviour needs to change:
Mobility is a key lever for climate action, yet many people stick with cars out of convenience. Bike-sharing systems are expanding, but often remain underused.
Why? Automated routines. People who commute the same route every day rarely question how they travel. Good alternatives get overlooked—not because of resistance, but because of habit. This is where behavioural science comes in.
The Green Nudge:
A field experiment by Behavioural Insights Team (BIT) in Portland for Biketown tested whether timing could unlock greater behaviour change. The nudge was simple: a flyer promoting the city’s bike-sharing scheme. But who received it made all the difference. For long-term residents, sign-up rates were just 0.31%. For people who had recently moved house, the exact same flyer boosted sign-ups to 1.14%—nearly four times higher.
Why? Moving disrupts routines. Without old habits in place, people are more open to rethinking how they get around.
BIT’s insight: Communication timed to „moments of change“—relocation, retirement, starting a new job—taps into naturally heightened openness. These brief windows make low-effort nudges far more effective–an “outsized” (unexpectedly large) impact for such a small intervention. Simply targeting the right “when” can dramatically improve results.
The results: 4x more sign-ups for the bike-sharing programme among newly moved households–from the exact same flyer. The only difference? Smart timing. This finding has since shaped mobility campaigns across multiple cities, demonstrating how behaviourally-informed segmentation boosts uptake without raising costs.
The Business Case: Targeted communication during periods of transition
Increases conversion rates by 3–4x
Reduces waste and overall marketing costs
Enables segmented, high-impact campaigns
Amplifies the effect of existing programmes—without additional resources
This principle applies across many sustainability contexts: energy advice when buying a home, plant-based offers in the first week of school, public transport information when starting a job. Addressing behaviour at the right moment saves budget and accelerates transformation.
Do you know other examples where timing made the decisive difference? Get in touch: hello@green-nudges.com
From Annalena Sommer from the Green Nudges Consulting team, featuring an intervention by the Behavioural Insights Team—a UK-based social purpose company specialising in the application of behavioural science to public policy. Founded in 2010 within the UK Cabinet Office, BIT now operates internationally, advising governments, cities and organisations on evidence-based interventions.
