Crash barriers are everywhere on the roads for the purpose of protecting you and other people from catastrophic car crashes. But how come these metallic structures protect us when they themselves look like an obstacle?
It is because they’re carefully designed and engineered. Every curve, joint, and material choice has a purpose. When a vehicle loses control, these barriers take the hit, absorb as much energy as they can, and steer the car away from even greater danger. Let’s take a closer look at how crash barriers work.
What happens during a crash: The science of collision
The story of collision revolves around energy and forces. Every moving car has kinetic energy. When you press the brakes, the system converts the car’s kinetic energy into heat through the brake pads and their friction with the road.
This process gradually slows the car down until it comes to a stop. This is why you feel a forward jolt when you suddenly hit the brakes. Your body wants to keep moving even as the car slows down. Your momentum continues until the seat belt or dashboard stops you.
But in a crash, there’s no smooth stop. The car’s kinetic energy has to be spent in an instant. The deformation of the car, the injuries and all the tragic consequences are the result of this energy conversion. The priority is to save the humans, which means finding ways to use up as much of the energy as possible before it reaches them.
This requires utilising the kinetic energy somewhere else. In most cases, the crash uses the car’s kinetic energy to deform both the vehicle and the crash barrier; crumpling metal, shattering glass, and sending parts flying. Every bit of destruction is the car’s way of soaking up energy so that less of it reaches the people inside.
You might have heard the argument that old cars were built stronger. They didn’t use to crush like modern cars during a collision. However, the old cars transferred all the kinetic energy to the passengers, resulting in horrific injuries and loss of lives.
That’s why engineers design modern cars to crumple on impact. This way, the car absorbs the kinetic energy through deformation, reducing the force that reaches the passengers.
How crash barriers work
Barriers look simple: a steel guardrail along a highway or a row of concrete blocks on a bridge. However, engineers carefully design these simple-looking structures to absorb impact, control the vehicle’s motion, and reduce the forces that reach the people inside during a crash.
When a vehicle crashes, the crash barrier works in the following three ways:
1. Absorb the Energy
A good barrier is designed to bend, flex, or even break apart on impact. This deformation absorbs a huge portion of the car’s kinetic energy. Crash cushions and water-filled crash barriers work on this principle; they absorb the energy and momentum of the car, stopping it and minimising the impact on the passengers.
However, not all barriers defrom. Concrete barriers are rigid and don’t flex at all. Though they still protect the vehicle in the other two ways.
Learn about different types of crash barriers and their application.
2. Redirect the Vehicle
The crash barriers guide the vehicle back onto a safer path, ensuring they don’t cross over to the other side of the road or bounce back into the traffic.
This is achieved through the design of the barriers. The curves in W-beam guardrails and the angle and shape of the concrete barriers are responsible for redirecting the car and preventing rollovers.
3. Control the Stop
The most important role of a crash barrier is to stretch out the crash in time. By flexing and dragging the car along its length, the barrier slows the vehicle down more gradually than a sudden, brutal stop would. This process is called gating.
It allows a vehicle that has hit the end of a barrier to pass through or run along it, rather than stopping instantly. It’s a way to absorb energy and guide the vehicle so that a high‑impact collision becomes survivable.
Design and Placement of Crash Barriers
Engineers calculate and design every aspect of a crash barrier from its height, width, and material to its angle, length, and spacing. They plan each detail so the barrier responds exactly as intended when a car hits: by absorbing energy and guiding the vehicle away from danger.
For example, they use vertical concrete barriers on bridges to prevent rollovers. The shape and angle of the concrete barrier control the movement of the vehicle.
If not carefully designed and tested, the crash barriers can themselves become a danger. Consider the fish tail ends. Though still used in certain places, they were widely used in the 60s. They distribute the impact forces well; however, hitting a car on these ends can lead to catastrophic results, as the sharp ends can penetrate the car.
A similar example is of buried terminals. Though there was zero chance of penetration, the ends could result in rolling over a high-speed car.
According to MASH, the crash barriers are now designed and engineered with three main targets:
- They shouldn’t flip the car
- The car shouldn’t be able to go over the barrier
- The barrier or its elements should not penetrate the car.
Secure Your Roads With Certified and Tested Crash Barriers
When a vehicle loses control, only a second or two determines the outcome. In those critical moments, it comes down to how well the road has been designed to protect its users.
Crash barriers form a crucial part of that design. Legend Hire offers certified crash barriers that are MASH tested and rated. These crash barrier designs have undergone real crash tests and are compliant with Australian Standards.