The number of US pedestrians who have been killed or badly injured while wearing headphones has tripled in six years, according to a study published Tuesday.
The annual tally rose from 16 in 2004 to 47 in 2011, bringing the total of cases to 116 over this period, say the authors.
More than half of the incidents involved pedestrians who were run down by trains.
Two-thirds of the victims were males and under the age of 30.
The research, published in the British journal Injury Prevention, was headed by Richard Lichenstein of the University of Maryland Hospital for Children in Baltimore.
The paper warns of "inattentional blindness" when wearing headphones, meaning a distraction that lowers the resources the brain devotes to external stimuli.
The trawl of US accident statistics covered iPods, MP3 players and other musical devices. It did not include mobile phones.