A new U.S. study looking at pedestrians who were killed or injured while wearing headphones finds that the incidents appear to be on the rise.

The study's lead author, Dr. Richard Lichenstein, says he began the research after hearing of a local teen who died while crossing railroad tracks. The teen was wearing headphones and didn't hear the oncoming train, even though it blasted its horn before hitting the boy.

"As a pediatric emergency physician and someone interested in safety and prevention, I saw this as an opportunity to -- at minimum -- alert parents of teens and young adults of the potential risk of wearing headphones where moving vehicles are present," Lichenstein said in a news release.

So Lichenstein, the director of pediatric emergency medicine at the University of Maryland Medical Center, gathered colleagues at the University of Maryland to search for reports of accidents involving people wearing headphones.

The team searched databases such as the U.S. Consumer Product Safety Commission, as well as media reports in Google News Archives, looking for accidents between 2004 and 2011.

They found 116 reports of death or injury of pedestrians wearing headphones. Of them, 81 were fatal.

The majority of victims were male under the age of 30, and almost nine out of 10 cases were in urban areas.

A full 55 per cent of the accidents involved trains, and almost three in 10 cases mentioned that the trains or cars involved in the crashes blew their horns but were not heard.

The researchers found that during the seven-year study period, the number of such cases tripled – a finding that worries them and bears further study, they said, particularly since the use of cellphones and MP3 players is increasing.

"The risks posed in use of these devices by drivers are well documented, but little is known about the association between headphone use and pedestrian injury," write the researchers in the journal Injury Prevention.

The researchers say there are a few reasons why headphones with handheld devices might pose a safety risk to pedestrians.

The first is that the devices can cause "inattentional blindness," meaning multiple stimuli divide the user's attention. The distraction is intensified by sensory deprivation, as the sounds coming through the earphones mask the sound of the train or car horns.

The researchers note there were a number of limitations to their study -- primarily that it relied heavily on media reports. Media outlets likely over-publish fatal events but tend not to run stories on non-fatal accidents, the authors note.

As well, the authors weren't able to distinguish how many of the accidents involved suicidal intentions, substance abuse or mental illness – all of which might have played a role in some of the incidents.