Modes Series - Light Metros & People Movers

Not every corridor is ripe for heavy rail rapid transit. Maybe the ridership isn't high enough to justify the capital costs. Maybe the grades and curving radii make standard heavy rail rapid transit vehicles impractical. Regardless of the means, this means one thing - if the corridor still deserves grade separated rapid transit, a Light Metro, also known as a Medium Capacity Rail System or Light Rapid Transit (in ASEAN countries), is the solution.

But to describe Light Metro systems in the modern context, we need to talk about the rise of the Automated People Mover and automated rail systems in general.

The Automated People Mover (APM) describes itself just from the name. It's automated, requiring no human driver. And it moves people, often within a small area with frequent stops or between a few key locations. They're lightweight, come in a wide variety of shapes and forms, and are very popular in airports and other spread-out complexes. For the purposes of this blog post, we're excluding inclined elevators, funiculars, and gondola lifts from this category since we treat them differently on this website.

People Mover cars are short and narrow (e.g. Bukit Panjang Innovia APM 100 C801A is 12.8m x 2.8m, compared to a North-South Line 23.5m x 3.2m C151C). They can make sharp turns due to the short length of each car. Being fully automated allows for incredibly frequent headways without the need to hire drivers for the frequency and means that the driver's cab area can be reallocated to passengers. And in the developed world where labor costs are heigh, this is a major boon - no driver means that the only costs to increase frequency are those of electricity and maintenance, and so people movers can be very convenient for riders.

Of course, it's not all good with people movers. They are great at what they do, but there is a wide variety of incompatible and proprietary people mover technologies, and if using them for meaningful mass transit, there are a wide variety of ways to do a spectacularly bad job. In the United States, this is exemplified by the Jacksonville Skyway, which goes nowhere and is set for conversion into the U2C (a Personal Rapid Transit gadgetbahn system that will run in mixed traffic and will therefore get stuck in the traffic that rapid transit is designed to avoid), and the Detroit People Mover, which runs in a single direction loop with poor connections to other modes of transit.

Now that we've talked about the benefits of people movers and lightweight systems, let's talk about Light Metro systems. First, we need to get one of the terminology issues out of the room - when I refer to a Light Metro system, I'm referring to lines purposefully built or renovated to lighter specifications in terms of train car size and total platform length. And when I use the term 'lighter', I mean it in a relative sense - lighter when compared to heavy rail rapid transit in the same geographic or cultural region. In other words, the Norristown High Speed Line's single car platforms are light when compared to the Market-Frankford Line, but Cleveland's Red Line is not light compared to the Chicago L since they just don't have the demand to fill the full length of the platforms. That being said, we are also going to add in a further restriction for when we use Light Metro as a term on this website - rolling stock (individual cars) must be either Light Rail Vehicles or rolling stock that is narrower/shorter than in comparable networks. In other words, Singapore's Circle and Downtown lines are considered heavy rail Rapid Transit despite using short trains, because they use the same heavy rail rolling stock as the other lines, just in shorter configurations. This conflicts with the definition used on Wikipedia, but works better for our site.

Benefits of Light Metro systems when compared to heavy rail rapid transit? Besides the ones mentioned earlier for people movers, if you can hit your capacity requirements with shorter trains running frequently, you can save on capital costs by downsizing stations - especially for tunneled stations, this is a massive reduction in capital costs. But that's not all - when running an elevated line, short, light trains means that the guideway is cheaper to construct, allowing for very cheap above-ground construction when compared to a heavy rail rapid transit system. Say that you have two proposals - first, an automated heavy rail rapid transit line with 8 cars that runs every 8 minutes to meet peak projected demand, and second, an automated light metro line with 2 cars that runs every 2 minutes to meet peak projected demand. The light metro option has the same capacity as the heavy rail option, but has far lower upfront capital costs and is much more convenient for the average user due to high frequency meaning less time waiting. Of course, if demand is going to outpace what a light metro can handle even at short headways, a full metro system with longer trains should be built if the alignment allows for it, or the light metro system should be built from the start with extra platform and depot space to allow for an extra car or two to be added like was done in Taipei.

In our definition, we mentioned shorter/narrower rolling stock as a requirement. Oftentimes, light metro lines use custom rolling stock. For example, people mover rolling stock may be used - think Crystal Mover, Véhicule Automatique Léger (VAL), and Innovia. Alternatively, light rail vehicles (both high floor and low floor) can be used, as well as heavy rail rolling stock with narrow loading gauges (and therefore narrower tunnels) in short train configurations.

Modern light metro systems began with VAL systems in France and New Transit/Automated Guideway Transit systems in Japan, with Lille Metro (1983) and the Port Island Line (1981). Non-automated Light Rapid Transit systems sprung up primarily in Southeast Asia, with the Manila LRT-1 opening in 1984 and subsequently exceeding its maximum design capacity. The first low floor LRV based Light Metro opened in Sevilla (2000). Systems continue to be built, especially in small medium-density European cities and in Southeast Asia.

We've talked a lot about modern automated people movers and light metro systems, but it's also worth taking a step back - after all, the terms Light Metro, Medium Capacity Rail System, and Light Rapid Transit are all fairly new as a mode.

The most famous of the 'original' light metro systems is undoubtedly the Glasgow Subway. Opened in 1896, it was built with short trains, ran with short trains, and still runs with short trains. It is the third oldest underground rapid transit system in the world, and works well even today. What is perhaps more interesting is that many of its contemporaries share many characteristics with modern light metro systems. The Liverpool Overhead Railway ran short trains as well, and early rapid transit systems (New York, Paris, Budapest, etc) started out with narrower cars. In fact, even New York City's IRT cars are narrower than light rail vehicles, and Paris Metro's initial lines have loading gauges similar to modern tramways in the same city. Of course at this time platforms tended to be longer than trains since trains operated in whatever length was needed to meet capacity, but the comparison still holds.

What separates these older systems from light metro systems today is primarily platform lengths. While Budapest's system remains a light metro, the New York City and Paris systems all exceeded design capacities and platforms were lengthened significantly.

As there is no standard definition for what constitutes a light metro, it's harder to give examples besides the VAL systems pioneered in France and the Automated Guideway Transit systems of Japan (both of which have lines and other applications that fall into people mover territory). However, some systems are quite notable.

First, the case of the Norristown High Speed Line. This was a commuter railroad that operated interurban services. The combination of single car trains, onboard fare payment, high platforms, complete grade separation, and third rail electrification make it so unique that it actually fits perfectly into the 'Light Metro' category because there is no other line in the United States that runs such short heavy rail trains.

Another shoutout goes to the Tyne and Wear Metro, which is unique not only for its typeface but also for being a rare case of a light metro that shares track with intercity railways and has grade crossings. Of course the shared track sees light use from the other railways and the grade crossings give the trains priority, ensuring that service quality is high.

Finally, a special mention to the Moscow Metro Butovskaya Line (12), which is often credited with the term 'Light Metro' to begin with.

Light Metro systems have enjoyed incredible growth over the past few decades, and their lower capital costs coupled with the proliferation of fully automated metro systems means that they will prove to be a common solution across the world. With the Montréal REM and massive Light Rapid Transit expansions in Jakarta in the works, we expect further improvements and innovations in the Light Metro space.