Outlier bias: AI classification of curb ramps, outliers, and context

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Technologies in the smart city, such as autonomous vehicles and delivery robots, promise to increase the mobility and freedom of people with disabilities. These technologies have also failed to “see” or comprehend wheelchair riders, people walking with service animals, and people walking with bicycles—all outliers to machine learning models. Big data and algorithms have been amply critiqued for their biases—harmful and systematic errors—but the harms that arise from AI's inherent inability to handle nuance, context, and exception have been largely overlooked. In this paper, I run two machine learning models across nine cities in the United States to attempt to fill a gap in data about the location of curb ramps. I find that while curb ramp prediction models may achieve up to 88% accuracy, the rate of accuracy varied in context in ways both predictable and unpredictable. I look closely at cases of unpredictable error (outlier bias), by triangulating with aerial and street view imagery. The sampling of cases shows that while it may be possible to conjecture about patterns in these errors, there is nothing clearly systematic. While more data and bigger models might improve the accuracy somewhat, I propose that a bias toward outliers is something fundamental to machine learning models which gravitate to the mean and require unbiased and not missing data. I conclude by arguing that universal design or design for the outliers is imperative for justice in the smart city where algorithms and data are increasingly embedded as infrastructure.