Automated Guideway Transit (AGT)
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№02
What Makes AGT Unique Among Exclusive Guideway Systems
2025/07/28
In our previous column, The Role of AGT in Urban Public Transportation, we explained how exclusive guideway systems—of which AGT (Automated Guideway Transit) is a part—offer significantly higher safety, punctuality, and speed compared to non-exclusive guideway systems such as buses and streetcars.
One often-cited feature of AGT within the category of exclusive guideway systems is its ability to handle steep gradients—up to 6%. While this is indeed noteworthy, it's not entirely unique; conventional railways can also manage 6% grades if equipped with sufficiently powerful motors. As long as the cost of such motors is justified by the benefits they bring, that solution can be viable.
However, what truly sets AGT apart—something that cannot be achieved by other systems—is its ability to navigate extremely tight curves, with a minimum turning radius of just 30 meters.
For example, there's a stretch between Shimbashi Station and just before Hamamatsucho Station where the Tokaido Shinkansen and the Yurikamome AGT line run side by side.
After departing Shimbashi, the Yurikamome executes a 90-degree turn at Shiodome, runs parallel to the Shinkansen, then makes another 90-degree turn toward the bay area, and one more 90-degree turn—forming a crank-like path through the high-rise buildings.
Similarly, between Hamamatsucho and Tamachi Stations, the Tokaido Shinkansen runs parallel with the Tokyo Monorail, which also makes a 90-degree turn toward the bay after diverging from the Shinkansen.
The Shinkansen, as Japan’s premier intercity rail system, runs as straight as possible. In contrast, urban transit systems like AGT and monorails are capable of making 90-degree turns along existing roadways.
Subways, which also serve urban areas, often follow the paths beneath major roads and feature similar 90-degree turns, as can be seen on route maps (though the routes themselves are not visible to the eye).
Unlike subways, however, elevated urban transit systems like AGT and monorails must turn 90 degrees at intersections without impacting nearby buildings. To meet this requirement, AGT systems are designed to handle extremely tight curves with a minimum turning radius of just 30 meters.
In contrast, monorails have a minimum turning radius of about 50 meters, which makes it difficult for them to turn 90 degrees without encroaching on surrounding structures.
This key difference highlights a major advantage of AGT over monorail systems.
AGT vehicles are also much shorter than typical railway cars—around 8 meters long compared to roughly 18 meters for conventional trains. This compact length allows AGT vehicles to make tight turns at intersections without requiring the removal of surrounding buildings.
If you tried to build an elevated railway above existing roads, changing direction at intersections would likely require the demolition of nearby structures. This makes underground construction a necessity for most new urban rail lines.
For lower-capacity corridors, LRT (light rail transit) is sometimes considered as an alternative to subways. However, since LRT shares road space, it reduces available lanes for cars and may negatively affect road traffic.
AGT was developed precisely to address this issue. It makes use of the space above existing roads without reducing road capacity, and it can turn at intersections without disrupting surrounding buildings.
For reference, Tokyo Metro’s Ginza Line has cars about 16 meters long with a minimum turning radius of 94 meters, while the Marunouchi Line uses 18-meter cars with a minimum radius of 140 meters. In general, small-radius curves in railways produce loud squealing noise, making them undesirable except in subways. For new above-ground rail lines, the minimum turning radius is typically set at 400 meters, with 200 meters accepted only in unavoidable situations.
From this, it’s clear just how exceptional AGT’s 30-meter turning radius really is.
Notably, you can observe these tight turns on the Port Liner just after departing Sannomiya Station and on the Nippori-Toneri Liner just past Nippori Station—both execute 90-degree turns on elevated tracks over road intersections.
Monorails, with vehicle lengths around 15 meters, require a minimum radius of at least 50 meters. This makes 90-degree turns over intersections without impacting adjacent buildings much more difficult. For instance, Tokyo Monorail makes a sharp turn near Minato City Sports Center by Tamachi Station, but the line encroaches on surrounding property to do so.
In short, the short vehicle length of AGT is not arbitrary—it is a critical design feature that enables it to make sharp 90-degree turns over intersections without disturbing nearby structures.
The 30-meter minimum turning radius is a defining characteristic of AGT—one not found in conventional rail or monorail systems.