Source: University of Maryland
quote: These accidents were due to both being distracted by their devices and blocking the sounds of the warning systems with their headphones
quote: Also, since this is a retrospective case series, neither causation nor correlation can be established between headphone use and pedestrian risk. Such risk can be determined only in virtual environments or large-scale pedestrian observational studies. However, we believe our grading system shows strong circumstantial evidence that headphones may have played a role in most injuries and deaths in the case series.