The number of car accidents related to smartphones has doubled over the past three years with the rise in the use of mobile digital devices, according to a research institute.

The Traffic Climate and Environment Research Center, a research unit of Hyundai Marine & Fire Insurance Co., said in a report it released Wednesday that the smartphone-related accident rate increased 1.9-fold from 437 in 2009 to 848 cases in 2012.

The abrupt rise in such accidents is attributed to both phone calls and the use of content-based functions on smartphones, such as music players, Internet browsers and instant messengers, the research center suggested.

These accidents mostly involve pedestrians staring at their smartphones while walking, as well as drivers distracted by smartphones while driving.

The majority, or 59 percent, of accidents involving pedestrians distracted by smartphones occurred between 10 a.m. and 6 p.m.

About 39 percent of the accidents involving distracted drivers took place between 6 p.m. and midnight.

In a separate report, the researcher also pointed out that smartphone users in their 20s were distracted by the devices the most, citing their research on 5,000 pedestrians strolling near Gangnam Station and Gwanghwamun Station, two of the most crowded areas in Seoul.

About 46 percent of these young pedestrians, the report stated, used their smartphones while walking, becoming engrossed in Internet browsing, messaging and listening to music.

The research center warned that pedestrians using smartphones while walking are more at risk of car accidents, since honking cars would need to be closer for them to notice.

The number of smartphone users totaled about 36 million as of September 2013, and the tech-driven country is expected to see the number continue to rise.

By Chung Joo-won (joowonc@heraldcorp.com)