Seoul tightens nighttime brightness limits on outdoor billboards

Advertisements on digital billboards light up Gwanghwamun Square in central Seoul's Jongno District, Feb. 5. Korea Times photo by Shim Hyun-chul

The Seoul Metropolitan Government has set stricter nighttime brightness limits on large LED billboards across the capital in response to concerns over visual fatigue among pedestrians and drivers.

The move followed The Korea Times' Feb. 7 report that glare from large digital displays can interfere with nighttime driving, leading to an increasing number of complaints over light pollution.

The city government said Tuesday it has come up with detailed regulations on brightness caps for outdoor LED billboards. In Korea, each local government is required to set its own regulations on outdoor advertising brightness and color.

According to the rules, the daytime brightness cap — the first daytime limit among local governments — is set at 7,000 candelas per square meter. The 7,000-candela daytime threshold was drawn from field data and international standards after consulting with industry and experts, the city said, noting it still allows for adequate on-site visibility.

For night, the limits are further tiered by display size and hour, ranging from 350 to 500 candelas — all well below the current ceiling of 1,500. Signs between 30 and 225 square meters are classified as medium-sized, while those exceeding 225 square meters are considered large.

From one hour after sunset to midnight, caps are set at 500 candelas for medium signs and 400 for large ones; after midnight, the limits tighten to 400 and 350, respectively.

The city set the caps based on a survey of 52 billboards conducted between January and March. The regulations will apply to all billboards 30 square meters or larger starting Wednesday.

The regulations also address content practices, urging operators to use scenes with low brightness and gradual frame transitions and to minimize bright flashes. The measures are also expected to cut energy consumption by roughly 15 percent, the city said.

“These standards are not a blanket crackdown on billboard brightness, but a rational improvement that balances advertising readability, visual comfort for citizens and energy efficiency,” said Choi In-kyu, head of the city's Design Policy Bureau, adding that the city will continue working to make Seoul's streets safer and more visually comfortable.

Seoul began to expand large billboards following a government push to create urban landmarks and promote the outdoor advertising industry through billboard-filled spaces modeled on New York's Times Square. Starting with Coex in Gangnam District in 2016, authorities steadily expanded designated free-display zones — where billboard regulations are relaxed — to include Gwanghwamun Square and Myeong-dong. Some buildings there now hold screens exceeding 1,200 square meters.