Elevated Lightrail System, South Korea

Innovative transport system improves public space

In the fall of 2018 the architectural studio ZJA welcomed a delegation of South Korean researchers, engineers and contractors that the South Korean Railroad Research Institute (KRRI) had sent on a fact-finding mission. They were interested in the ZJA designs for the Randstad Rail station Beatrixlaan in The Hague and the Lightrail station at The Hague Central Station.

Not much later an invitation arrived to participate in a research project for an innovative lightrail system, that would provide a long-term solution for the increasing problems of an overburdened road system and the consequent nuisance of noise, air pollution and unsafety in the densely populated metropolitan areas of South Korea.

Quest for innovation

What the South Korean authorities were looking for was a true innovation, an upgrade in quality. They sought a lightrail system that had a functional and economically viable design, but that most of all could be considered as an improvement of public space. First by introducing a comfortable, clean and safe mode of transport, but also by the visual appeal of its viaducts and stations. Around the stations there was to be plenty of room for greens and cafés and shops for people to enjoy their stay. The wish was for a transport system that could be implemented in all South Korean metropoles, and was top quality in terms of engineering, functionality, aesthetics and urban planning.


Elevated tracks

The requirements that the new South Korean system had to meet were ambitious.  As an underground track on this scale was too costly, an elevated double track was applied here. But then with enough elevation and with as little number of outstanding columns as possible so that the area close to the tracks does not see its quality of living deteriorate or impaired. This asked for an elevation of 15 meters and columns that are placed not less than a staggering 200 meters apart. The entire construction was required to have an as slender and light design as possible. An additional requirement was the roof covering the entire track to exclude problems with snow during the winter. Then there was the visual experience to be considered of people in the offices and apartment buildings close to the tracks, of the passengers on the trains as well as of the people in the street, in traffic. Obviously, the design was expected to be as energy efficient, sustainable and easy to maintain as possible. To minimize noise in the densely populated city the trains have rubber tires.

The design

The columns supporting the viaduct are Y-shaped. The arms that support  the double track are spread about 30 meters apart, 15 meters above the ground. The steel structure in between the tracks is the backbone of the construction. A capital “I” is the best description of the shape of the combination of deck and structure: at the bottom is the plateau with the tracks, above it is the primary structure of the roof. This results in an always unhindered view of the city for the train passengers sitting on the right side.

To prevent the 200-meter wide span sagging under its own weight ZJA chose to apply a hybrid construction. First there are the supporting arms of the columns, and then the central backbone of steel trusses in a continuous X-shape that add stiffness. Next the roof and its network of outriggers. This openly designed network of steel tubes includes pre-tension steel cables, making sure all the weight adds to optimising the stiffness of the viaduct, while the look of the viaduct retains its lightness and transparency. 


In the architectural design of the roof and the network of outriggers the emphasis lies on organic lines and curves. The roof has an important function in the distribution of forces into the construction and that is why it raises itself in a gentle waive at each column. The viaduct elevating the train is a white and friendly undulating wave gliding through the city. Thanks to the wavy rhythm the appearance of weightlessness is created.

The lighting plan

The roof has a glass covering with optional PV-cells to supply the energy for the lighting of the tracks and viaduct. When developing such an extensive addition to the already dense urban structure the visual impression it makes after sundown is of great importance. For that reason, ZJA developed a sophisticated lighting plan, that first of all lights the tracks for the train driver and the passengers from the centre. It also sees to the lighting of the underside of the tracks and the roof, in such a way that the organic lines and the rhythm in the network of tubes are highlighted. The columns, painted in a light grey colour, in contrast to the white of the steel tubing, have their own lights. The result is a pleasant and soft spacious effect, emphasizing the floating effect of the design.

An asset for the city

Old elevated railway tracks were notorious for their excruciating noise, the shadow and stench and unwanted vibrations they brought. They were bulky obstacles that took away quality of life from the neighbourhood. This contemporary design for South Korea however is an asset for the city. Its design radiates transparency and spaciousness, brings less noise and traffic and more space for trees and pedestrians.

ZJA’s design for the Elevated Lightrail Transit System is a light and lively volume; an open, delicate looking network that undulates gently through the metropolis. Sitting on the train that glides effortlessly and swiftly through the city offers an unhindered view of a bird in flight. An experience that offers quietness and pleasure. Living in a neighbouring building and looking down on the transparent undulating roof and seeing the light play over the trusses and the tubes, one wishes for a moment to be aboard that carriage, weightless among the towers. It is a sight that seems to lift one up, sparking a desire to fly like a bird in a soundless flight, whether one is in one of the towers, on the street or on the platform, with the train approaching.

Nomination: Architizer A+Award 2024

Architect: ZJA
Client: GS E&C and the South Korean Railroad Research Institute (KRRI)
In collaboration with: Woosung D&C, Dong-A Engineering and C & SC CO
Structural design: SIDstudio, IV-Infra
Year: 2019 - present

Project: #1142



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