The Bosphorus Bridge (Turkish: Boğaziçi Köprüsü) spans the waters of the Bosphorus Strait, exemplifying contemporary engineering and underscoring Turkey’s significant geographic and cultural location. The 15 July Martyrs Bridge (Turkish: 15 Temmuz Şehitler Köprüsü) is the southernmost of the three suspension bridges connecting Europe and Asia in Istanbul. In conjunction with the Fatih Sultan Mehmet Bridge and the Yavuz Sultan Selim Bridge, it constitutes a vital conduit for transportation and commerce, effectively connecting the continents. It extends from Ortaköy on the European side to Beylerbeyi on the Asian side, enabling the transit of millions and representing the cohesion of a metropolis that spans two continents.

The Bosphorus Bridge, a gravity-anchored suspension bridge, features a complex design marked by tall steel structures and slanted hangers. The aerodynamic deck is supported by sturdy steel cables, creating a prominent outline against the Istanbul skyline. The bridge measures 1,560 meters (5,118 feet) in length and has a deck width of 33.40 meters (110 feet), showcasing an imposing yet graceful design. The principal span between its massive towers is 1,074 meters (3,524 feet), and these towers reach a remarkable height of 165 meters (541 feet). The bridge features a clearance of 64 meters (210 feet) above sea level, facilitating the transit of large marine boats between the Black Sea and the Sea of Marmara.

Upon its completion in 1973, the Bosphorus Bridge was celebrated as an engineering achievement, ranking as the world’s fourth-longest suspension bridge span. At that time, only the Verrazano-Narrows Bridge, the Golden Gate Bridge, and the Mackinac Bridge exceeded its length. For almost ten years, it held the title of the longest suspension bridge in Europe, a record unbroken until the Humber Bridge was completed in 1981. It maintained its designation as the longest suspension bridge in Asia until the Fatih Sultan Mehmet Bridge, the Second Bosphorus Bridge, assumed the title in 1988, succeeded by the Minami Bisan-Seto Bridge in 1989. Although it is no longer one of the longest suspension bridges in the world, it continues to be an essential and historically important construction, currently positioned 40th internationally in span length.

In addition to its architectural magnificence, the Bosphorus Bridge has observed significant historical occurrences. One of the most spectacular events transpired on the night of 15 July 2016, during the unsuccessful military coup d’état attempt. A contingent of troops seized control of the bridge, obstructing traffic and entering a protracted confrontation that would ultimately become a pivotal milestone in contemporary Turkish history. To commemorate those who perished opposing the coup, the Turkish government formally designated the bridge as the 15 July Martyrs Bridge on 25 July 2016. This classification converted the bridge from a simple transportation conduit into a symbol of national resilience and solidarity.

The Bosphorus Bridge is an essential transportation artery, crucial to Istanbul’s dynamic infrastructure. Daily, numerous vehicles navigate its breadth, linking the European and Asian sectors of the city with remarkable efficiency. The bridge, a pivotal point on the O-1 highway, supports commuters and enhances trade, logistics, and tourism, thereby solidifying Istanbul’s position as a worldwide nexus. At night, its brilliant lights create a captivating radiance over the strait, reinforcing its reputation as both a functional marvel and a symbol of the city’s vitality.

The Bosphorus Bridge: A Historic Link Between Continents

A Symbol of Connection

The Bosphorus Bridge (Turkish: Boğaziçi Köprüsü) traverses the glistening waters of the Bosphorus Strait, exemplifying modern engineering and underscoring Turkey’s significant geographic and cultural significance. The 15 July Martyrs Bridge (Turkish: 15 Temmuz Şehitler Köprüsü) is the southernmost of the three suspension bridges connecting Europe and Asia in Istanbul. In conjunction with the Fatih Sultan Mehmet Bridge and the Yavuz Sultan Selim Bridge, it constitutes a vital conduit for transportation and commerce, effectively connecting the continents. It extends from Ortaköy on the European side to Beylerbeyi on the Asian side, enabling the transit of millions and representing the cohesion of a metropolis that spans two continents.

Engineering Marvel and Structural Grandeur

The Bosphorus Bridge, a gravity-anchored suspension bridge, features a complex design marked by tall steel structures and slanted hangers. The aerodynamic deck is supported by sturdy steel cables, creating a prominent outline against the Istanbul skyline. The bridge, measuring 1,560 meters (5,118 feet) in length and 33.40 meters (110 feet) in deck width, is both imposing and graceful. The primary span between its massive towers is 1,074 meters (3,524 feet), and these towers reach a remarkable height of 165 meters (541 feet). The bridge features a clearance of 64 meters (210 feet) above sea level, facilitating the transit of large marine boats between the Black Sea and the Sea of Marmara.

Record-Breaking Achievements

Upon its completion in 1973, the Bosphorus Bridge was celebrated as an engineering achievement, ranking as the world’s fourth-longest suspension bridge span. At that time, only the Verrazano-Narrows Bridge, the Golden Gate Bridge, and the Mackinac Bridge exceeded its length. For almost ten years, it held the title of the longest suspension bridge in Europe, a record unbroken until the Humber Bridge was completed in 1981. It maintained its designation as the longest suspension bridge in Asia until the Fatih Sultan Mehmet Bridge, the Second Bosphorus Bridge, assumed the title in 1988, succeeded by the Minami Bisan-Seto Bridge in 1989. Although it is no longer one of the longest suspension bridges in the world, it continues to be an essential and historically important construction, currently positioned 40th internationally in span length.

A Site of Historic Events

In addition to its architectural grandeur, the Bosphorus Bridge has observed significant historical occurrences. One of the most spectacular events transpired on the night of 15 July 2016, during the unsuccessful military coup d’état attempt. A contingent of troops seized control of the bridge, obstructing traffic and entering a tense confrontation that would ultimately become a defining milestone in contemporary Turkish history. To commemorate those who perished opposing the coup, the Turkish government formally renamed the bridge the 15 July Martyrs Bridge on 25 July 2016. This classification converted the bridge from a simple transportation conduit into a symbol of national resilience and solidarity.

An Indispensable Artery of Transport

The Bosphorus Bridge is an essential transportation route, crucial to Istanbul’s dynamic infrastructure. Daily, numerous vehicles navigate its breadth, linking the European and Asian sectors of the city with optimal efficiency. The bridge, a pivotal point on the O-1 highway, accommodates commuters while simultaneously enhancing trade, logistics, and tourism, so solidifying Istanbul’s status as a worldwide nexus. At night, its brilliant lights create a captivating radiance over the strait, reinforcing its reputation as both a functional marvel and a symbol of the city’s vitality.

The Bosphorus Bridge: A Historical Journey from Conception to Completion

First Bridge Proposals

The concept of connecting the Bosphorus, the natural boundary separating Europe and Asia, has fascinated sovereigns, builders, and engineers for thousands of years. The initial documented endeavor dates to the rule of Persian King Darius I (522–486 BCE). In his battle against the Scythians, Darius commissioned the architect Mandrokles to design a bridge of ships, an inventive floating structure created by aligning vessels side by side and interlinking them with planks. This basic yet efficient crossing enabled his army to cross the strait.

Subsequent to this historical undertaking, deliberations concerning a permanent bridge over the Bosphorus remained inactive until the 16th century. In 1503, the polymath Leonardo da Vinci presented an ambitious plan to Sultan Bayezid II. His letter delineated a bridge intended to across the Golden Horn and maybe continue across the Bosphorus; however, the proposal remained unactualized.

In 1900, a French engineer named Arnaudin proposed a railway bridge. He proposed two sites: one connecting Sarayburnu to Üsküdar, and another joining Rumeli Hisarı to Kandilli. Neither design received approval. Simultaneously, the Bosphorus Railroad Company presented a proposal for a steel suspension bridge embellished with architectural motifs influenced by North African architecture. Despite its esthetic appeal, the project known as “Hamidiye” did not receive the approval of Sultan Abdülhamid II.

The Republic era experienced a resurgence of interest. In 1931, Turkish entrepreneur Nuri Demirağ partnered with the American Bethlehem Steel Company to design a suspension bridge similar to the Oakland Bay Bridge in San Francisco. The concept encompassed a length of 2,560 meters, incorporating a railway and tram system. Notwithstanding continuous endeavors, the project was ultimately unachieved.

By the mid-20th century, global engineering companies focused on the Bosphorus. In 1951, German architect Paul Bonatz performed a feasibility study at the request of the Krupp business. His team designated Ortaköy and Beylerbeyi as optimal sites; nonetheless, the project did not advance. In 1953, the Turkish government commissioned a study by De Leuw, Cather & Company, which confirmed the feasibility of a suspension bridge. Notwithstanding successive offers and proposals, financial and logistical limitations persisted in hindering the endeavor.

In 1958, Steinman, Boynton, Granquist, and London developed an additional proposal for a suspension bridge. Nevertheless, administrative obstacles hindered its implementation. In the same year, the German company Dyckerhof und Widmann proposed an innovative tension bridge using prestressed concrete decks supported by offshore piers. Aesthetic considerations prompted an advisory council to dismiss this design, reinforcing the desire for a suspension bridge that would complement the Bosphorus skyline.

The Construction Process

Following decades of contemplation, technological progress in the 1960s ultimately facilitated realization. In 1967, the Turkish government solicited proposals from four foreign engineering firms. In 1968, the British firm Freeman, Fox & Partners received the contract, while a German-British collaboration, consisting of Hochtief AG and Cleveland Bridge and Engineering Company, secured the construction bid.

The inaugural ceremony occurred on February 20, 1970. Excavation began at the Ortaköy and Beylerbeyi locations, establishing the foundations for the bridge’s imposing support pillars. As of August 4, 1971, the assembly of the tower was in progress. In January 1972, the inaugural guide wire was installed across the strait, signifying a crucial milestone in the project.

The complex procedure of hoisting steel cables commenced in June 1972, with engineers diligently adjusting tension and alignment. By December, the initial bridge deck was elevated into position. Employing an exact swing mechanism, parts were elevated by cranes and secured to suspension wires. The final deck was constructed on March 26, 1973, establishing a continuous connection across continents for the first time in history. The 60 deck parts were subsequently welded together, facilitating the inaugural successful pedestrian crossing from Asia to Europe.

In April 1973, the asphalt-laying phase began, employing a robust rubber-composite combination to guarantee durability. By June 1, the road surface was finalized, preceded by the construction of approach viaducts in May. On June 8, engineers performed the inaugural vehicular crossing test, validating the bridge’s structural integrity.

Inauguration and Legacy

On October 30, 1973, President Fahri Korutürk officially inaugurated the Bosphorus Bridge, marking the 50th anniversary of the Republic of Turkey. The bridge, finished in under three years, incurred a cost of around $21.77 million. Upon its inauguration, it was the longest suspension bridge outside the United States, exemplifying architectural prowess and global cooperation.

In addition to its architectural excellence, the bridge transformed Istanbul’s connectedness, promoting economic development and urban growth. Over time, its importance beyond mere functionality, becoming into a lasting emblem of unification among continents and civilizations. Renamed in 2016 as the July 15 Martyrs Bridge to commemorate those who defended democracy during the unsuccessful coup attempt, the structure continues to serve as a crucial component of the city’s transportation infrastructure.

Bird’s Eye View of the July 15 Martyrs Bridge (2011)

The July 15 Martyrs Bridge, an architectural masterpiece spanning the Bosphorus Strait, features a sophisticated and graceful design. This suspension bridge, anchored by two enormous pillars, serves as a crucial link between the European and Asian sides of Istanbul. Each support tower of the bridge, measuring 165 meters in height, exemplifies engineering accuracy and is constructed from soft yet resilient high-strength steel. The towers consist of two vertical box-section legs, supported by three horizontal beams, ensuring structural integrity and visual attractiveness. The bridge deck is suspended between two towers by suspension cables that cover a central distance of 1,074 meters, an extraordinary engineering achievement for its era.

The bridge deck, with a width of 33.40 meters, comprises 60 rigidified, hollow sheet panel pieces welded to form a continuous and robust surface. These devices are both useful and enhance the bridge’s aesthetic appeal. The deck’s surface is upheld by the lowest horizontal beams of the towers, ensuring stability and flexibility under the substantial weight of traversing traffic. The bridge, rising 64 meters above sea level at its apex, facilitates six traffic lanes—three in each direction—and features pedestrian pathways on side consoles that are 2.70 meters wide.

A key characteristic of the bridge’s engineering is the utilization of slanted suspension cables. The July 15 Martyrs Bridge, originally inspired by the Severn Bridge in the United Kingdom, underwent substantial modifications to address safety concerns related to metal fatigue. The slanted suspension cables were ultimately substituted with linear ones, so augmenting the bridge’s resilience. These structural modifications illustrate the evolution of the bridge’s design to address the challenges posed by rising traffic levels while preserving its iconic status.

Traffic

The July 15 Martyrs Bridge is not just a significant monument but also an essential element of Istanbul’s transportation infrastructure. Crossing the Bosphorus, it enables the daily transit of thousands of cars, linking the European and Asian sections of the city. The bridge was originally projected to accommodate significantly fewer vehicles than it currently does, with initial estimates forecasting approximately 32,000 daily crossings at its inauguration in 1981. By 1987, daily traffic reached 130,000 crossings, and by 2004, it escalated to 180,000, indicating the exponential growth of Istanbul’s population and urban development.

In reaction to the increasing traffic volume, restrictions have developed over time. In 1991, heavy-tonnage vehicles, excluding buses, were prohibited from traversing the bridge to mitigate structural deterioration. Currently, the bridge facilitates municipal and public buses, automobiles, and motorbikes, while pedestrian access has been prohibited since 1978 to maintain safety and efficiency of the crossing. In 2024, the bridge had an impressive 71.8 million vehicle crossings, highlighting its essential function in Istanbul’s everyday activities.

Vehicle Crossings of Bridges

The July 15 Martyrs Bridge, like other critical infrastructure such as the Fatih Sultan Mehmet Bridge and the Yavuz Sultan Selim Bridge, is essential to Istanbul’s traffic management. In 2024, the road experiences a daily average of over 430,990 vehicle crossings, making it one of the most heavily trafficked in the city. This figure exceeds the daily crossings of the more recent Yavuz Sultan Selim Bridge, which documented 57,927 daily crossings. Vehicle traffic on the July 15 Martyrs Bridge has consistently risen, from 394,840 daily crossings in 2009 to exceeding 400,000 in 2014. The bridge’s pivotal function in Istanbul’s transportation system is demonstrated by these data, which indicate its sustained significance and the city’s swiftly growing infrastructural demands.

Istanbul Marathon

The July 15 Martyrs Bridge serves as a vital transportation conduit and a prominent symbol for significant cultural and athletic events, like the Istanbul Marathon. The marathon, conducted yearly, features a route that traverses the Bosphorus Bridge, establishing it as the race’s most pivotal crossing point. Founded in 1979, the Istanbul Marathon has developed into a distinguished event, drawing participants from throughout the world. The marathon has been designated a Gold Category event by the International Association of Athletics Federations (IAAF) and is regarded as one of the premier marathons globally.

The event provides a distinctive experience, allowing participants to traverse between Europe and Asia without the typical impediments of traffic. The Istanbul Marathon features various categories, including a full marathon, a 15 km race, and a 10 km race, celebrating both athleticism and the cultural richness and unity of Istanbul. The bridge’s crucial part in this event reinforces its significance as a symbol of the city’s history and its future ambitions.

Lighting

The visual allure of the July 15 Martyrs Bridge transcends its architectural form, attributed to its exquisite lighting design. Inaugurated in 2007, the bridge’s lighting system is among the most sophisticated globally, with 16 million color-changing LED bulbs. These energy-efficient LEDs offer both utilitarian and aesthetic illumination, augmenting the bridge’s allure while reducing environmental impact. The installation of the lighting system required meticulous design and implementation, including nearly 7,000 meters of cable and 2,000 LED light modules precisely arranged to produce a stunning visual effect.

The lighting system is not only a display but also a demonstration of Turkey’s creative engineering and technical expertise. The installation process was a significant accomplishment, requiring rope access technicians to execute almost 9,000 meters of vertical rappelling to finalize the project. The outcome is a stunning visual phenomenon that converts the bridge into a radiant beacon across the Bosphorus each night, enhancing the magnificence of an already renowned edifice.