Dutch cities installed rain sensors at traffic lights that automatically shorten waiting times for cyclists during wet weather.
Cycling rates drop when it rains. Precipitation is one of the strongest negative predictors of cycling frequency. Even moderate rainfall leads to statistically significant ridership declines (Kane & Kythreotis, 2024). Not because people don’t want to cycle, but because bad weather magnifies every small friction point. Standing at a red light in the rain feels longer and more uncomfortable than it ever does on a dry day. For many, that discomfort is enough to reach for the car keys.
And yet this is the exact moment when infrastructure design can make a difference. Rain doesn’t have to mean a worse cycling experience.
Cities including Rotterdam, Groningen and Enschede have installed rain sensors at key intersections, particularly along school routes. When the sensor detects rainfall, the algorithm automatically adjusts and cyclists get the greenlight sooner and wait less.
The intervention works on two levels: it reduces objective discomfort, and it signals something more powerful: the city is on your side, even when the weather isn’t. In Rotterdam, a small indicator light on the traffic pole makes the system visible to cyclists. This matters. It transforms an invisible infrastructure change into a felt experience, reinforcing cycling identity (Thaler & Sunstein, 2008; Akerlof & Kranton, 2000).
The logic is simple: car drivers are dry. Cyclists are not. So when it rains, cyclists get priority.
The Results: Rotterdam’s evaluation shows cyclist waiting time drop from 48 seconds to 33 when sensors are active – a 31% reduction (Gemeente Rotterdam, n.d.). Car waiting times increase modestly, from 21 seconds to 29. In Amersfoort, 28% of surveyed cyclists said they would cycle more often with smart light infrastructure, and 20% said they would leave their car at home (Gemeente Amersfoort, n.d.). In Rotterdam, bike traffic has grown 10% in the past year alone with rain sensors among one of the 40 measures fueling that momentum.
The Business Case: The Netherlands moves on bikes, accounting for over 27% of all trips nationally. When rain pushes cyclists towards cars, that modal share doesn’t vanish: it moves onto roads already strained. Every percentage point lost to the car means more congestion, more emissions, more pressure on infrastructure never designed to absorb it. At €5,000 per intersection, the rain sensor is one of the cheapest ways a city has to protect the modal mix it has spent decades building.
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From Annalena Sommer from the Green Nudges team, highlighting one of 40 measures from Rotterdam’s local government to stimulate cycling.
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