Classification Drives Geographic Bias in Street Scene Segmentation

Previous studies showed that image datasets lacking geographic diversity can lead to biased performance in models trained on them. Most prior works have studied geo-bias in general-purpose image datasets (e.g., ImageNet, Open-Images) using simple tasks like image classification. Recent works have studied geo-biases in application-based image datasets like driving datasets. However, they have only focused on coarse-grained localization tasks like 2D or 3D detection. In this work, we investigated geo-biases in a Eurocentric driving dataset (Cityscapes) on the fine-grained localization task of instance segmentation. Consistent with previous work, we found that instance segmentation models trained on European driving scenes (Eurocentric models) were geo-biased. Interestingly, we found that geo-biases came from classification errors rather than localization errors, with classification errors alone contributing 10-90% of the geo-biases in segmentation and 19-88% of the geo-biases in detection. Our findings suggest that if a user wants to directly apply region-specific models (e.g., Eurocentric models) globally, they may prefer to coarsen label categories (e.g., use a common label like 4-wheelers over labels like car, bus, and truck). Coarser labels can reduce classification errors, which, as we show in this work, is a major contributor to geo-bias.