What are highway rails called? Guardrails, Barriers, and More Explained
If you've ever driven on a highway, you've undoubtedly seen them: those metallic or concrete structures that line the edges of the road and separate opposing lanes. You might call them "highway rails," but what's the official or most common terminology for these essential safety features? The answer isn't a single word, as different types of "rails" serve different purposes and have distinct names.
The Most Common Term: Guardrails
When most people refer to the wavy metal barriers that run along the sides of highways and overpasses, they are usually talking about guardrails. These are arguably the most ubiquitous type of highway rail. Their primary function is to prevent vehicles from veering off the road, falling from elevated sections, or colliding head-on with oncoming traffic. They are designed to absorb and redirect the impact of a vehicle, minimizing damage and injury.
Types of Guardrails
Guardrails themselves come in a few variations:
- W-Beam Guardrails: These are the most common. They feature a characteristic "W" shape formed by a single steel panel. This shape provides strength and helps to cradle and redirect errant vehicles.
- Thrie-Beam Guardrails: A more robust version of the W-beam, the Thrie-beam has a more complex profile with three "ribs" instead of two. This makes them stronger and better suited for areas with higher impact risks or heavier vehicles.
- Cable Guardrails: Instead of solid beams, these systems use tensioned steel cables stretched between posts. They are highly effective at absorbing energy and can reduce the severity of impacts. They are often found in median barriers.
Beyond Guardrails: Other Highway Rail Systems
While "guardrail" is the most common term, there are other types of "rails" or barriers found on highways, each with its own specific name and purpose:
Median Barriers
These are structures placed in the median (the central dividing strip) of a highway to prevent vehicles from crossing into opposing lanes of traffic. Median barriers are crucial for preventing devastating head-on collisions.
- Concrete Barriers (Jersey Barriers): These are probably the most recognizable type of median barrier. They are made of concrete and have a distinctive sloped shape. This shape is designed to redirect vehicles upwards and back into their own lane, rather than allowing them to vault over.
- Steel Barriers: Similar in function to concrete barriers, these can be made of steel, often in a more rigid design.
- Cable Barriers: As mentioned earlier, cable systems are also frequently used as median barriers due to their energy absorption capabilities.
Bridge Rails and Parapets
When you're driving over a bridge or overpass, the structures along the edge are specifically designed to prevent vehicles from going over the side. These are often referred to as:
- Bridge Rails: This is a general term for any railing system along the edge of a bridge designed for safety.
- Parapets: A parapet is a low protective wall along the edge of a bridge, balcony, or roof. On bridges, they can be made of concrete or metal and serve the same purpose as guardrails in preventing vehicles from falling.
Traffic Barriers
This is a more encompassing term that can include guardrails, median barriers, and other types of structures designed to manage or redirect traffic and prevent accidents. Traffic barriers are a broad category of safety devices.
Crash Cushions (Impact Attenuators)
While not strictly "rails," these are also highway safety devices that might be confused with them. Crash cushions are often placed at the ends of concrete barriers or other fixed objects to absorb the impact of a vehicle. They are designed to crumple and dissipate energy, reducing the force of the collision.
In summary, while "highway rails" is a perfectly understandable descriptive term for the average person, the more specific and technically accurate names depend on the type and location of the safety feature. Most commonly, you're referring to guardrails, but understanding terms like median barriers and bridge rails provides a more complete picture of highway safety engineering.
Frequently Asked Questions (FAQ)
How are guardrails designed to redirect cars?
Guardrails, particularly W-beam and Thrie-beam types, are engineered with specific shapes and tension. When a vehicle impacts the rail, the "W" or multiple ribs of the beam deform and flex, absorbing some of the kinetic energy. The curved design of the rail and its posts also works to lift and redirect the vehicle's momentum back towards its lane, rather than allowing it to continue off the road or into another lane.
Why are concrete barriers (Jersey barriers) shaped the way they are?
The iconic sloped shape of a Jersey barrier is intentional. The lower, wider base provides stability, while the sloped upper section is designed to lift the tires of an impacting vehicle. This lifting action, combined with the barrier's mass, redirects the vehicle upwards and back into its original lane. The shape minimizes the chance of the vehicle vaulting over the barrier or snagging on its top edge.
Why are different types of highway rails used?
The selection of a specific type of highway rail depends on several factors, including the potential severity of impacts, the speed of traffic, the likelihood of different types of vehicles (e.g., cars vs. trucks), and the surrounding environment. For instance, cable barriers are excellent at absorbing energy and preventing rollovers, while concrete barriers are robust and effective in high-impact areas like medians. Each type is chosen to provide the optimal level of safety for its intended location.
