More pedestrians are being hit by cars and trains while listening to music on their iPods, a national study shows.

According to research from the University of Maryland School of Medicine , serious injuries to pedestrians listening to headphones, mostly under age 30, have more than tripled in six years. 

The study of 116 accident cases from 2004 to 2011 revealed that in 70% of the cases, they were killed. More than two-thirds of victims were male and under the age of 30. More than half of the moving vehicles involved in the accidents were trains, and nearly a third of the vehicles reported sounded a horn prior to the crash. 

The study was initiated after a teenager was killed crossing railroad tracks. The teen was wearing headphones and did not avoid the oncoming train despite honking.

Earlier this month, authorities say a man wearing headphones unknowingly walked into the side of a moving NJ Transit train in north Jersey, but escaped with only minor injuries.

The Tri-State Transportation Campaign's ten year study finds that alarmingly, 1 in 5 traffic deaths in New Jersey are pedestrians.