The cleanliness of Basel's streets is measured using a computer system that analyzes video from street-sweeping vehicles, detecting and classifying litter to calculate a Cleanliness Index (CI) on a scale from 0 to 5. The Grand Council has set a target for the city to maintain a CI of at least 4.5.

In March 2026, the city's street cleanliness was monitored across 4,836 street sections, resulting in 133,282 individual measurements. The overall cleanliness was high, with an average CI of 4.73. The cleanest street section achieved a perfect score of 5.0, while the lowest recorded was 3.42. A significant 89.4 percent of all measurements met or exceeded the required threshold of 4.5, leaving 10.6 percent below this target.

The districts with the highest average cleanliness were Riehen, Wettstein, Bachletten, Breite, and Gotthelf. It is important to note that Riehen's ranking is based on a very small sample of only 2 street segments. The districts with the lowest average scores were Matthäus, Klybeck, Clara, Gundeldingen, and Altstadt Kleinbasel. The ranking of districts can change depending on the metric used; for instance, while Matthäus has the lowest average CI, its percentage of measurements above the threshold is higher than some other districts in the bottom five. The full details for all districts are available in Tables 1 and 2.

Comparing the first month of data, January 2024, to the most recent data from March 2026 shows a clear positive trend. The percentage of measurements rated as good, meaning a CI of 4.0 or better, increased from 98.8 percent to 99.8 percent. More importantly, the percentage of measurements exceeding the council's 4.5 threshold rose substantially from 67.8 percent to 89.4 percent. This consistent upward trend, illustrated in Figure 1, indicates that street cleanliness in Basel is not just stable but is demonstrably improving over time.