The main purpose of a highway guardrail along the highway is to form a safety barrier to help protect a motorist who has drifted off the road.
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If a car is running off the road for one reason or another, the best thing that can happen is for that car to come to rest unimpeded.
Sometimes, however, that is not possible and that is where guardrails come in.
In certain places on any given stretch of road, the roadway might have steep embankments or side-slopes next to it, or even be lined with trees.
Utility poles, bridge piers and retaining walls are other obstacles. In these cases, striking a guardrail would be greatly preferable to striking the obstacles, so guardrails are usually installed.
They lessen the severity of a potential crash and make the roads safer.
The guardrail can act in a myriad of ways from deflecting a vehicle back onto the road, slowing it down or stopping it, or in some cases just slowing it down enough and allowing it to proceed past the guardrail.
Guardrails are not a 100% failsafe, but they do help.
Obviously the size of the vehicle and the speed with which it hits the highway guardrail plays a part in how effective the guardrail is in slowing a vehicle.
Before guardrails are installed, engineers weigh all the potential factors to make sure that the placement works as well as possible in all conditions.
The guardrail itself functions as an entire system rather than just stand-alone pieces. Each piece serves a different purpose as part of the whole. Everything from the posts that are driven into the ground to the way the guardrail connects to the post is important and plays a part.
The end terminal and the anchoring system at the end terminal is just as important. But overall, the highway guardrail basically consists of two key parts; the guardrail face and the end terminal.
A guardrail system is always put through performance tests before it is actually installed along a roadway. The performance of the system is assessed through crash tests that are done in a controlled environment. You can click here to see more about Highway Guardrail Performance direct from the Federal Highway Administration
Safety professionals use certain criteria to determine if the system meets standards.
The guardrail face test is used to determine if a car is directed back onto a roadway when it meets the rail.
The end treatment tests are then conducted by having a vehicle strike the rail dead-on and also at an angle. This will determine if the system is properly absorbing energy from a vehicle.
For head-on impacts, the end treatment should absorb most of the energy so that the guardrail can gate or extrude, and the vehicle can pass through.
This will slow the vehicle down as it passes behind the guardrail, allowing it to come to rest with minimal damage.
The tests used to test a guardrail system are usually conducted at about 60 MPH, so it is important to understand that if a vehicle hits the guardrail at higher speeds, the system may not operate properly.
Very high speeds are especially troubling because guardrail systems are simply not meant to accommodate vehicles traveling far above posted speed limits.
The faster the vehicle is going when it strikes the guardrail, the more damage might occur because the energy demonstrated is so much more.
Even a guardrail system that is working at peak performance can only absorb so much energy.
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A guardrail is a type of road safety device, often referred to as a traffic barrier, which is installed at dangerous sections of roads, whether on urban, rural or highway sections. Read on for more information about this traffic barrier type, including:
See more information about the Armco barrier here.
It’s a type of traffic barrier, specifically designed to protect motorists from direct impact with hazardous objects on the side of the road and beyond the barrier, and to prevent vehicles from leaving the safe travel path.
It consists of several components like the W-beam shaped steel panels attached to wooden or steel posts, which are buried into the soil or attached to a hard surface by means of bolts. If placed in the median of two highways, then the panels are on both sides of the wooden or steel posts. The end of the barrier is buried or fitted with an end terminal, which is a solid plate.
It provides a safety edge to the end section of the barrier to prevent the sharp edge of the panel from penetrating the body of a vehicle that collides with the end of the barrier.
These safety or traffic barriers are installed at the edge of rural and urban roads, in the medians of two opposite flowing highways, at the on and off-ramps on highways leading towards or away from tollbooths, and on bridges.
As road safety barriers, these act to improve road safety conditions. This is achieved in the following ways:
The entire system works together to absorb the kinetic impact energy of a vehicle collision with the guardrail. The impact energy is disbursed along the length of the barrier, thereby giving it the necessary crash impact absorption capacity. Some of the impact energy is transferred from the vehicle and its occupants to the barrier. This helps to reduce the force of impact on the vehicle and its occupants.
If a vehicle collides with an unforgiving object like a wall or tree that doesn’t absorb part of the impact energy, the full force of impact is taken by the vehicle. Reducing the impact force on the vehicle helps to reduce the level of damage to it. In turn, this can also help to reduce the impact injuries of the occupants.
These barriers also act to redirect vehicles back to their original path and to slow them down. For example, when a motorist falls asleep behind the wheel, and the vehicle careens off the road, a slight bump with an object can cause the driver to wake up.
Although not guaranteed, if the vehicle hits the barrier at an angle from the side, the bump can be enough to steer the vehicle along the length of the barrier, causing a friction sound. This sound and bump can help to wake the motorist, giving the driver time to correct their error without the vehicle leaving the safety of the travel path altogether.
The friction caused between the vehicle’s body and the steel from the W-beam can help to slow down the vehicle.
The height of the barrier should be selected according to the ground clearance, weight and speed of vehicles using the particular section of road.
Although manufacturers may differ in the design of their products, specific local and international standards apply for the quality of work, materials and design. With the safety of road users in mind, it’s imperative to choose a supplier able to provide these barriers in compliance with such standards.
The section lengths of the beams range from 3,81 to 4 metres per beam. These beams are made to be used on straight and curved areas, proven in the design that allows for curving to fit a radius from 3 to 45 metres.
Each beam is made according to the requirements of SANS 1350 with end terminals available in bullnose and end-wings. The steel sections are available as uncoated or galvanised according to SANS 121 / ISO 1461.
The posts are available in steel or creosoted treated timber, with the timber types conforming to the requirements of SANS 457, available in bevelled or domed tops.
Delineators for optimal visibility, are available for attachment to the beams. These delineators come in V and D shapes and are made from Chromadek for longevity. The slotted base design facilitates easy attachment.
W-beam guardrails are durable traffic barriers, made in accordance with specific international and local manufacturing, product safety and quality standards.
These barriers are durable, easy to maintain, able to redirect vehicles, and absorb and disburse kinetic impact energy from a collision.
More information about W-beam guardrails and pricing is available from Armco Superlite in South Africa. Reach out for a quote and product specifications.
The company is the world’s best guard rail wholesale supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.