How to prevent large ships from colliding with bridges?

With the continuous development of science and technology and the economy, various bridges spanning rivers and lakes have emerged. The Wuhan Yangtze River Bridge, the first road-rail bridge built across the Yangtze River after the founding of the People's Republic of China, is also one of the country's important historical landmarks, known as the "First Bridge Across the Yangtze River," and a symbol of China's bridge construction. This year, the bridge is 66 years old. But did you know that due to navigation conditions and ship handling, the Wuhan Yangtze River Bridge has been struck more than 70 times, most of which occurred in the 1990s? Even so, the bridge has not shifted or sunk to this day. Bridge experts have stated that with scientific maintenance, the bridge, originally designed for a 100-year lifespan, can be used for another 50 years. The unwavering strength of the First Yangtze River Bridge is a source of pride for China's infrastructure, and it is also protected by an active collision avoidance system. Recently, the Wuhan Yangtze River Bridge successfully conducted a live-ship test of its active collision avoidance warning system. How does this system provide warnings? What "magic weapon" does the First Yangtze River Bridge possess to prevent large ships from colliding with the bridge?

How busy is the Yangtze River waterway? Is the risk of a ship colliding with a bridge high?

Before understanding the bridge active collision avoidance warning system, we need to understand the Yangtze River main channel where the First Yangtze River Bridge is located. How busy is this channel? And how high is the risk of a ship colliding with a bridge? The Yangtze River main channel stretches over 2,800 kilometers from Shuifu Port in Yunnan Province to the Yangtze River estuary, carrying an enormous volume of traffic and experiencing heavy navigation.The daily ship traffic in the Wuhan section of the Yangtze River is around 400 times, and the annual traffic is around 140,000 times. Therefore, the ship traffic is relatively large, and the probability of ships passing under bridges is also relatively high, which poses a risk of ship collisions with bridges.

What are the functions of an active bridge collision avoidance and early warning system?

There are 11 bridges spanning the Yangtze River in the Wuhan section, six of which are located in the 18-kilometer core area of Wuhan Port, forming the largest bridge cluster in the middle and lower reaches of the Yangtze. All six of these bridges are now equipped with active bridge collision avoidance and early warning systems.

Its main function is to remind ships to take timely precautions against three potential hazards when passing under a bridge. The first is the deviation of a ship from its course; if a ship deviates, it may collide with the bridge piers. The second is exceeding the height limit. We know that every bridge has a certain clearance for navigation. Exceeding this clearance increases the risk of collision with the bridge structure. The third is that ships in the bridge area may not follow established navigation rules, such as turning around or anchoring.

The most direct early warning system is the use of a flashing light and a loudspeaker installed on the bridge. Once the warning is triggered, the flashing light and loudspeaker will sound and flash continuously, allowing the crew to see the alarm signal on the bridge immediately and alert them. This is the first layer of warning. The second layer is through sound. Each vessel has a corresponding radio station, which is required to be on duty during navigation. Our system will broadcast the warning information on VHF channel 06 in a timely manner, allowing the crew to adjust their navigation accordingly.

How does the bridge's active collision avoidance warning system work?

To test the functionality of the bridge's active collision avoidance warning system, the Wuhan Maritime Safety Administration arranged a field test. Under the direction of staff, a cargo ship began to deviate from the normal navigation channel of the Wuhan Yangtze River Bridge.

The electronic map demarcates deviation warning zones; the yellow areas represent our warning zones. If a vessel enters a yellow zone, its Automatic Identification System (AIS) will send its position signal to our system in real time. We then consider it to have deviated from the main channel, and navigating within the yellow zone poses a certain risk of collision with the bridge piers. A radar system is also installed on the bridge to scan and locate vessels. If the vessel's AIS malfunctions and cannot send location signals, the radar system on the bridge can serve as a backup.

Shortly after the test cargo ship deviated, the active collision avoidance warning system quickly detected the deviation. Warning lights installed on the Yangtze River Bridge began flashing, and the radio on the test cargo ship received a deviation alert from the system. Upon receiving the warning, the test cargo ship began to correct its course, and after returning to the correct channel, the system alert was lifted.

How does the early warning system determine "over-height" with just a glance?

Besides detecting deviations from course, another collision risk is vessels exceeding height limits. How does the bridge's active collision avoidance early warning system anticipate such risks? Experts explain that lidar devices are installed on the bridge to perform a 3D scan of the vessel and calculate its length, width, and height. Additionally, a water level gauge at the bottom of the bridge emits a beam towards the water surface, measuring the actual height of the bridge above the water. If the bridge can only accommodate vessels up to 30 meters tall, but the measured height exceeds 30 meters, the system will issue an audible and visual alarm to effectively warn and control the over-height vessel. Experts state that compared to the past, where only human visual judgment was relied upon for determining vessel height, this system offers significant improvements in accuracy and efficiency. With the application of new technologies, early warning systems will become increasingly effective in alerting vessels to dangerous behavior. However, we also urge drivers to navigate cautiously to ensure the safe operation of bridges and waterways.