Korean road wayfinding and how it can decrease user load in split-second decision situations.
You're doing 50 on Heolleung-ro in Seoul. The screen says 150 metres, the lane row shows six lanes, a sign goes by overhead in two languages and a bus fills your right mirror. Somewhere in that you have to work out which lane is yours. It's a design problem with a two-second budget.
Korea's answer is paint. I drove this stretch to Namhansanseong last week, and this is how the junction showed up on the car's navigation, rebuilt from my photos. Scroll it into view and it drives.
Look at what each part of that screen asks of you. The sign needs reading. The lane arrows need counting. The pink needs nothing. You've seen it before you've read a word. Then you look up through the windscreen and the same pink is on the road.
In March 2011 a car and a truck traded lanes at Ansan Junction on the Seohaean Expressway. Right after the toll gate the road split three ways, to Mokpo, Gangneung and Incheon, and the two needed to cross. An obstacle came up, the car swerved and the truck couldn't. Its driver died.
Yoon Seok-deok, an engineer at the Korea Expressway Corporation's Gunpo office, had been told to find a fix even children could understand. He found it at home, watching his kids play with crayons and paint. Colour the road.
It was against the law. Korean road paint came in four colours, white, yellow, blue and red, and anything else broke the traffic act. An engineer told him that if someone followed his line into a crash, he'd carry the blame, and that he wouldn't do it in his place. With a local police inspector on his side, Yoon painted Ansan anyway on 3 May 2011, by hand with rollers in traffic, while drivers rang all day to shout at him.
Ansan had averaged 25 crashes a year. From May to the end of December it had three. Yoon told the story to Money Today in 2024, and the government keeps it in its innovation archive.
It spread. The Expressway Corporation wrote its own rules in 2012, the transport ministry published a national manual in December 2017, and on 17 April 2021 the lines became official road markings. By March 2023 there were 905 on the expressways alone. Across the sites, crashes fell 27% once the paint went down, and Seoul's painted intersections had half the crashes in 2017 that they'd had in 2016. Yoon got a national medal for it in 2024.
Korea wasn't first. Sendai coloured whole lanes at its Aramachi junction in December 2008, red ochre and sky blue, with the overhead signs in matching colours, and crashes there fell by about 60%. What Korea added was a national system with rules anyone can learn in one drive.
The rules read like a design system, and that's the part I keep thinking about.
Two colours, each with one job. Pink when the road splits off one way. When it splits two ways, pink takes the direction further from the centre line and light green the nearer one, with full green allowed only where the tarmac is too pale for light green to show. A third colour would mean learning a legend at 50 km/h, so there isn't one.
Colour is seen before it's read. Your eye lands on a pink stripe in grey asphalt before you decide to look for it, the way it finds the one red dot among grey ones. A sign works the other way: you scan it, read it and match it to the lane. When the budget is two seconds, a cue the eye finds by itself is the only kind left.
The map and the world agree. Korean navigation tells you to follow the pink lane, the screen draws the lane pink, and the guidance manual puts the colour on the signs as well, next to the destination it leads to. Three surfaces carry one signal, so nothing needs translating between them.
The cue sits where your eyes already are. The sign is above you and the screen is down to your right. The paint is on the road ahead, the one place you're guaranteed to be looking.
Blue is the odd one out. It isn't in the guidance rules at all. Korea paints blue for lanes with rules of their own, like bus and Hi-Pass lanes, and picked the guidance colours to keep clear of it.
Here's the same screen with the paint taken off.
Most screens don't run on a two-second budget, but some moments do: a destructive confirm, a checkout with a timer, a dashboard someone glances at mid-task. In those I want one channel carrying the answer, one colour per choice, and that colour following the person from where they plan to where they act, the way the pink goes from the screen to the road.
And keep the system small enough to learn by using it. Korea stopped at two colours and wrote down when each one applies. The paint gets you there fast because you never had to hurry to read anything.