In this blog post, we’ll examine the differences between light rail—which has recently garnered significant attention—and conventional subways, as well as its types, pros and cons, and the feasibility of its implementation.

What is light rail?

Light rail is short for “lightweight rail” and refers to an electric rail system that is lighter than conventional heavy rail (standard subways) and tailored to meet smaller-scale demand. For example, Lines 1 through 9 in Seoul are all heavy rail systems.
In terms of transport capacity, light rail can handle approximately 5,000 to 40,000 passengers per hour, placing it between buses (1,000 to 5,000 passengers per hour) and heavy rail (30,000 to 70,000 passengers per hour). The goal of light rail is to transport smaller numbers of passengers more frequently, serving as a supplementary route in large cities or a main line in small-to-medium-sized cities.
In terms of cost, light rail construction costs are 50–80% lower than those of heavy rail; if underground construction is eliminated, construction costs can be reduced to about 30% of those for heavy rail. Additionally, labor costs can be reduced through designs that allow for unmanned operation or eliminate the need for station staff, and the application of technologies such as maglev or rubber-tyred systems results in lower noise and vibration, providing a smoother ride.

Types of Light Rail — Streetcars (Trams)

Streetcars, or trams, run on tracks laid on the road surface. Since they generally share the same surface as road traffic, they interact frequently with other modes of transportation, resulting in a relatively low average operating speed. Because they share the road with pedestrians and vehicles, a driver must be on board to respond to various road conditions.
Advantages include the ease of installing station facilities and infrastructure, as well as a low floor height that allows the elderly and people with mobility impairments to board and alight comfortably. Recently, catenary-free tram technology—which supplies power through steel tracks on the ground—has been developed. This trend eliminates the need for overhead power lines, thereby improving the urban landscape and addressing safety concerns.

Monorail: Suspended and Girder Types

Monorails, which use a single rail, are broadly categorized into suspended systems (where vehicles are suspended from the track) and girder systems (where vehicles run on a concrete track). Suspended systems can handle sharp curves and steep gradients relatively well, and their small support pillar cross-sections result in a smaller footprint. Additionally, construction periods are relatively short, making them advantageous when road occupancy must be minimized or traffic congestion needs to be alleviated quickly.
On the other hand, the suspended type requires taller support columns to maintain a consistent operating height, which increases material costs and makes the system vulnerable to weather conditions such as strong gusts of wind. The girder type offers higher speeds and greater transport capacity, and facilitates stable operation. While all monorails require no major elevated structures other than the track and support columns, their simple design makes it difficult to secure evacuation routes, posing a disadvantage in that escape outside the station is challenging in an emergency.
In South Korea, monorails are widely adopted for tourism purposes, and the Daegu Metro Line 3 (monorail type) is a prime example of their use as an urban transit system.

Maglev Light Rail

Maglev trains operate by floating above the track; since they do not come into contact with the track, they produce very little noise and vibration and are well-suited for high-speed operation. The principle involves using a linear motor to control the magnetic field by reversing the direction of the current flowing through a coil; as a result, the attractive and repulsive forces between the train and the track periodically change, generating propulsion.
In terms of speed, maglev systems can operate at high speeds averaging over 250 km/h. While they may be slightly less energy-efficient than wheeled systems, their maintenance costs are relatively low. Although the initial unit cost of the vehicles is about twice that of heavy rail, resulting in a significant upfront cost burden, an example of construction costs per kilometer of track—25 billion won for maglev, 30 billion won for light rail, and 50 billion won for heavy rail—shows that economic advantages may arise depending on the situation.
Overseas, maglev systems are in operation in countries such as Japan and Germany. In South Korea, there was an instance where the opening of a approximately 6.1-kilometer maglev project connecting Incheon International Airport to Yongyu Station was delayed due to technical issues.

Economic Viability, Implementation Cases, and Challenges

Some light rail projects have fallen short of initial expectations, sparking controversy over their economic viability. Notably, projects involving large-scale investments have been criticized for creating a financial burden due to “overestimated demand.” For example, some lines where demand was projected to be very high ended up with actual demand at less than half of the forecast, resulting in operational deficits.
Generally, in cities with a population of 1.5 million or more where major heavy rail lines are already in operation, it may be more efficient to strategically introduce light rail to bridge the demand gap between buses and heavy rail, rather than constructing an entire new line as heavy rail. In particular, utilizing light rail as a connecting line between new and old city centers or linking secondary city centers can enhance citizen convenience while avoiding excessive spending.
The decisive factors are not only the choice of technology or cost but also the accuracy of initial demand forecasts, operational plans, and the presence or absence of political interference. The introduction of light rail must be preceded by realistic planning that takes traffic patterns and urban structure into account, as well as a transparent feasibility study.

Conclusion

Light rail is a useful mode of transportation that can fill the gaps left by buses and subways, and various technical configurations can be selected to suit the conditions of each city. While its advantages—such as reduced construction costs, low noise and vibration, and high transport efficiency per unit—are clear, successful implementation requires realistic demand forecasts, route designs tailored to specific objectives, and rational decision-making free from political and financial considerations.