Packed rush hour trains, delays and unpleasant odors — all familiar headaches for seasoned rail riders. Yet for some, the daily commute includes a more sinister threat: gropers.

According to National Police Agency statistics, there were 4,250 cases of groping and other indecent assaults on trains in 2012, a 6.9 percent increase from the previous year.

To combat the problem, a long-standing issue for many women who ride trains as well as the people who operate them, a high school girl, herself a groping victim, and her mother have developed an idea to ward off sexual predators — a warning badge.