Akashi Kaikyo Bridge: The World's Longest Suspension Bridge

The Akashi Kaikyo Bridge, also called the Pearl Bridge, is the world's longest suspension bridge by central span, stretching 1,991 meters between its two main towers. It crosses the Akashi Strait, linking the city of Kobe on the Japanese main island of Honshu to Iwaya on Awaji Island in Hyogo Prefecture. Opened in 1998, it remains one of the supreme achievements of modern civil engineering.

For more than two decades the Akashi Kaikyo Bridge has stood as the benchmark against which every other long-span bridge is measured. It is a structure of superlatives — taller than the Eiffel Tower, strong enough to shrug off a magnitude 8.5 earthquake, and so long that the wire inside its cables could circle the planet more than seven times. This guide explains where the bridge is, how it was built, why its location made it one of the hardest construction jobs ever attempted, and what makes it a landmark of both Japanese geography and global engineering.

Where Is the Akashi Kaikyo Bridge?

The bridge spans the Akashi Strait (Akashi Kaikyo) in Hyogo Prefecture, in the Kansai region of western Japan. The strait is a narrow, deep channel that forms part of the Seto Inland Sea, the body of water separating Honshu from the smaller island of Shikoku. On the northern shore lies Kobe, one of Japan's busiest port cities; on the southern shore is Awaji Island, a stepping stone toward Shikoku.

Geographically, the location is treacherous. The strait funnels strong tidal currents that reach about 4.5 meters per second, sits in the path of frequent Pacific typhoons, and lies in one of the most seismically active zones on Earth, near the boundary where several tectonic plates interact. These conditions — fierce water, fierce wind, and fierce ground motion — combined to make the Akashi Strait one of the most demanding sites ever chosen for a major bridge.

Engineering and Record-Breaking Design

The Akashi Kaikyo Bridge is a three-span, two-hinged stiffening-truss suspension bridge with a total length of 3,911 meters. Its central span of 1,991 meters is flanked by two side spans of 960 meters each. The two main towers rise 298 meters above sea level, making them taller than the Eiffel Tower and among the tallest bridge towers in the world.

The structure is held up by two enormous main cables, each 112 centimeters in diameter. Every cable is bundled from 36,830 individual high-strength steel wires, and laid end to end the wire totals roughly 300,000 kilometers — enough to wrap around the Earth about 7.5 times. The cables carry a stiffened steel truss deck designed to stay rigid in extreme wind.

Two features make the design especially remarkable:

• Tuned mass dampers: Each tower contains a system of 20 pendulums weighing about 10 tonnes each. They swing out of phase with the tower's motion to cancel vibrations from wind gusts and earthquakes.
• Open-truss deck with slots: The deck uses a triangular stiffening truss with central gaps that let wind pass through rather than building up lift. This is what allows the bridge to survive winds of up to 286 km/h, the kind generated by powerful typhoons.

Together these innovations let an extraordinarily long and tall structure remain stable in some of the harshest natural conditions any bridge faces.

Construction History

The dream of spanning the Akashi Strait grew out of tragedy. In 1955, two ferry accidents in the strait killed 168 people, many of them children, and public pressure mounted for a fixed crossing. Decades of planning and feasibility studies followed before construction finally began in May 1986.

Building the foundations was a feat in itself. Engineers sank massive steel caissons, each about 80 meters in diameter, onto the seabed and filled them with specially formulated underwater concrete that could set despite the racing tidal currents. The two anchorages that grip the main cables required around 1.4 million cubic meters of concrete in total.

Cable spinning — shuttling wire back and forth across the strait between the anchorages — took roughly two years, with each wire precisely positioned so the load would distribute evenly. Then, on January 17, 1995, before the deck was hung, the Great Hanshin (Kobe) earthquake struck with magnitude 6.9, its epicenter almost directly between the two towers. The towers shifted apart, and engineers had to redesign the deck on the fly to fit the new geometry. The completed bridge opened on April 5, 1998, after 12 years of work and a cost of about ¥500 billion (roughly US$3.6 billion at the time).

Surviving the 1995 Kobe Earthquake

The bridge's encounter with the Great Hanshin earthquake is the most famous chapter in its story. The quake devastated Kobe and killed more than 6,000 people, yet the unfinished bridge survived. The seismic motion permanently widened the gap between the towers, lengthening the planned main span from 1,990 meters to 1,991 meters — the extra meter that gives the bridge its record-setting figure today.

Because the bridge had been engineered to withstand earthquakes far stronger than the one it experienced, the structure was not damaged. That real-world test, occurring mid-construction, became powerful proof that careful seismic design can stand up to nature's most violent forces — a lesson studied by bridge engineers worldwide.

Key Facts

• Location: Akashi Strait, Hyogo Prefecture, Japan (34.6167°N, 135.0226°E)
• Connects: Kobe on Honshu to Iwaya on Awaji Island
• Main span: 1,991 meters (world's longest for a suspension bridge)
• Total length: 3,911 meters
• Tower height: 298 meters (taller than the Eiffel Tower)
• Opened: April 5, 1998, after 12 years of construction
• Navigational clearance: 65 meters above sea level

Cultural and Economic Impact

The Akashi Kaikyo Bridge completed the Kobe-Awaji-Naruto Expressway, the easternmost of the three Honshu-Shikoku connection routes. By replacing slow ferry crossings with a continuous highway, it cut travel time between Kobe and Tokushima on Shikoku from more than two hours to roughly one, knitting the islands together economically and carrying around 23,000 vehicles a day. The one-way toll for a standard car is approximately ¥2,370.

The bridge is also a spectacle. At night it is lit by 1,084 high-intensity lamps capable of displaying 28 different color patterns that change with the seasons and holidays. Its pearl-like glow inspired the nickname "Pearl Bridge." Visitors can tour the Bridge Exhibition Center at the Kobe end to walk inside an anchorage and learn how the structure was built, and guided "Bridge World" tours even take the adventurous up the maintenance walkway to the top of a tower for sweeping views over the Seto Inland Sea.

How It Compares to Other Bridges

For 24 years the Akashi Kaikyo held the undisputed title of longest suspension span. In 2022 the 1915 Canakkale Bridge in Turkey opened with a main span of 2,023 meters, edging past it for the overall record. Even so, the Akashi Kaikyo remains the longest suspension bridge in Japan and in the Asia-Pacific region, and it is still regarded as a landmark moment in engineering — the structure that proved spans approaching two kilometers were achievable in earthquake and typhoon country. Its records for resilience under seismic load, rather than length alone, are what continue to set it apart.

Frequently Asked Questions

Is the Akashi Kaikyo Bridge still the longest suspension bridge in the world?

It held the record from 1998 until 2022, when Turkey's 1915 Canakkale Bridge opened with a slightly longer 2,023-meter span. The Akashi Kaikyo Bridge, at 1,991 meters, is now the second-longest suspension bridge in the world and remains the longest in Japan.

Why is it called the Pearl Bridge?

The nickname comes from its nighttime illumination. The bridge is lit by more than a thousand lamps that can produce 28 color patterns, often giving the structure a soft, pearl-like glow against the dark strait.

Can pedestrians walk across the Akashi Kaikyo Bridge?

The bridge is a road-only crossing and is not open to ordinary pedestrian or cyclist traffic. However, guided "Bridge World" tours let visitors walk along the maintenance catwalk beneath the deck and ride an elevator to the top of one of the 298-meter towers.

How did the bridge survive the 1995 Kobe earthquake?

It was designed to withstand earthquakes far stronger than the magnitude 6.9 that struck during construction, using tuned mass dampers and a flexible structural system. The quake shifted the towers apart and permanently lengthened the main span by about one meter, but caused no structural damage.