In the coastal zone of Cádiz, steel and concrete are forced to battle the harsh marine environment. Salt and wind here spare even the sturdiest structures: in ten years, unprotected metal can simply disappear. That’s why the Constitution of 1812 Bridge, the longest in Spain, has been under the constant watch of a digital monitoring system since its opening. Its structure is equipped with 525 sensors that record even the slightest changes around the clock.
Every day, thousands of cars and trucks cross this engineering giant, while ships and platforms pass beneath. The bridge has become a symbol of the city, but it also demands ongoing attention from specialists. A team of more than 30 people monitors its condition, working without days off. About seven million euros are allocated annually for its maintenance and safety—a figure rivaled only by the cost of maintaining the country’s largest tunnels.
The bridge is part of a small but strategically important section of the road network—just 14 kilometers in total—but home to two key crossings: the new bridge and the old Carranza, which for decades was the only way into the city. The challenging climate and heavy traffic make this stretch a real test for engineers.
Construction of the bridge began in 2008, though plans had been discussed for decades. It was only inaugurated in 2015, with the project cost exceeding half a billion euros. Despite demographic challenges in Cádiz, the bridge was deemed essential to serve a metropolitan area with over 700,000 residents and to support the development of the port.
Technically, the bridge is a complex combination of four different structural types. The most impressive section is supported by 176 steel cables anchored to two pylons, each 185 meters high. Climbing to the top of these towers is not for the faint-hearted: workers ascend weekly via internal staircases and elevators to inspect the structure and perform maintenance. In fact, even a falcon has chosen this height as a regular resting spot.
The main bridge control center is located in the San Pedro district of Puerto Real. Here, massive screens display data from all sensors: some measure tilt, others monitor the stretching or compression of materials, and others detect vibrations. The system is integrated with cameras, traffic lights, barriers, and lighting. Custom software developed for this site enables real-time monitoring of even the slightest changes. Power outages are not a concern—backup generators are in place.
In the event of an earthquake, special devices can block traffic to minimize risks. During ten years of operation, the bridge has withstood hurricanes with wind gusts over 100 km/h and has not required major repairs. The older Carranza causes more concern: in the spring of 2024 alone, more than three million euros were spent on its restoration.
The Constitution of 1812 Bridge is not just a transport artery, but an example of how modern technology and human effort can extend the life of complex engineering structures even in the harshest conditions.
