The Eshima Ohashi, is a rigid frame bridge 1.7 km long and almost 45 meters high, it was built from 1997 to 2004 to connect the cities of Matsue and Sakaiminato, in Japan. This bridge, which is in fact the steepest in the world, has become famous for the optical illusion created by telephoto lenses, which makes it appear much steeper than it actually is. In fact, this bridge appears to have a very steep ramp, so much so that it has been nicknamed the “Roller Coaster Bridge”. But isn’t it really that steep? Or is it just an illusion?
Why they call it the “Rollercoaster Bridge”: the slope that makes it unique
THE’Eshima Ohashi it is located in southern Japan and its name means Eshima Great Bridge, the islet where it starts from. The main reason why this bridge has become very famous online is its – at least apparently – extreme slope. Why apparently? Because technically yes, this bridge is truly the steepest bridge in the world because when it was designed on the small island of Eshima there wasn’t enough space available to create a ramp with a less steep slope than the actual one of the bridge. This slope is due to the height of the bridge, which allows ships to pass under it, without interrupting road traffic, as happened in the past.
Having said that, the slope you see in some photos is real, i.e. is this bridge really that steep? Actually no, the slope is also due to a perspective game. More precisely it has to do with the way these photos were taken, but to understand this I must first explain how a telephoto lens works. When you take a close-up photo with a wide-angle lens, which is a lens with a very wide viewing angle, objects in the foreground appear very large, while objects in the background appear small and distant. On the contrary, when you shoot from afar using a telephoto lens, having a very narrow viewing angle, the effect is the opposite: objects seem closer to each other, and the space between them is “squashed”.
Telephoto lenses greatly compress perspective, visually reducing the distance between objects. When the bridge is photographed with these lenses, the distance between the lowest and highest points appears to be much shorter, creating the illusion of an extremely steep climb. This optical effect deceives the human eye, amplifying the slope of the bridge. This phenomenon is called prospective compression. In the case of the bridge, its length appears to compress relative to its height, making the slope appear much steeper than it actually is. If you find yourself in those parts and want to get this photograph, you really have to move far away from the bridge, in fact you have to reach another island and from there you can get your photo of the “roller coaster” bridge.
How Eshima Ohashi was built
The Eshima Ohashi connects the cities of Matsue, Shimane Prefecture, and Sakaiminato, Tottori Prefecture. The construction of the bridge, which began in 1997 and completed in 2004, represents an extraordinary example of modern engineering. The fundamental characteristic of the bridge lies in the calculation of the slopes: the inclination of 6.1% on one side and 5.1% on the other – meaning more or less a slope of 3 degrees – allows passing vehicles to face the slope very easily. That is, it’s not like you have to go flat out to face the climb, let’s understand, also because as we said the bridge is not that steep. With a length of 1.7 kilometers and a maximum height of almost 45 metersEshima Ohashi is also the largest rigid frame bridge in Japan. Its rigid structure, with no moving parts, allows it to withstand heavy loads and distribute forces evenly, ensuring resistance and durability over time, essential characteristics in a region subject to earthquakes and typhoons. In fact, each pillar is designed to withstand shocks up to magnitude 7 on the Richter scale.
As I told you before, the bridge was created to facilitate both maritime and road traffic. In fact, before its construction, the two cities were connected by a drawbridge, a type of infrastructure which, although useful in the past, had obvious operational limitations. Every time a ship had to pass, the bridge rose, blocking road traffic for at least eight minutes. This constant interruption was a problem for citizens and for the flow of goods between the two areas. Furthermore, the old bridge could not support vehicles weighing more than 14 tons, creating further limitations for heavy transport. As traffic and economic needs in the region increased, it was clear that a new infrastructure solution was needed. Thus the idea of Eshima Ohashi was born.
read also: https://www.geopop.it/lelevato-interno-piu-lungo-al-mondo-si-trova-in-cina-ed-e-alto-326-metri
