Why Install a Road Safety Fence: What You Need to Know

With several types of barriers available to improve road conditions, why and when should you choose the wire rope safety fence? These and other questions regarding the barrier type are answered below to help you make an informed buying decision.

What is a wire rope road safety fence? armco safety fence

It’s a type of road barrier that is installed to improve road safety and reduce the severity of injury upon a vehicle’s collision with the barrier. The design includes wire rope cables attached to steel posts. The ropes are tensioned to create an effective barrier. Typically, it consists of three to four parallel wire ropes or two intertwined and two parallel wire ropes tensioned between posts.

What happens when a vehicle collides with the road safety fence?

The posts give way while the tensioned cables take the impact force of the collision, thereby directing it away from the vehicle and its occupants. The tensioned cables do most of the redirecting and absorb the kinetic impact energy from the colliding vehicle. The posts and cables work as a system to absorb the impact force and stop the colliding vehicle.

How safe is a wire rope safety fence?

The results of full-scale vehicle crash tests have shown that wire rope safety fences perform better in terms of lower vehicle occupant injury levels than rigid road barriers.

Although it’s not possible to guarantee zero injuries for any type of road safety product, the injuries road users suffer tend to be less severe in most instances in comparison with injuries suffered in collisions with other types of barriers.

The claim is supported by the results of research conducted at the Monash University Accident Research Centre. The researchers based their findings on the performance of the road safety fences next to the roads of Victoria. The study scope included a 100-km stretch of road. The results showed that the barriers reduce collision incidents and vehicles from leaving the safe travel path by up to 87%.

The report noted that rigid concrete road barriers are less effective in reducing the level of injuries. Wire rope safety fences outperform other barriers in terms of the reduction of the severity of injuries.

Why do wire rope fences perform better than rigid and semi-rigid barriers in terms of the number of injury incidents?

The design of these barriers makes it possible for the wire ropes to give way significantly, thereby reducing the impact force on the colliding vehicle and its occupants. The risk of vehicle penetration is drastically reduced whereas the risk is more notable with rigid barriers.

Where are wire rope safety fences installed?

These barriers are installed in urban areas, next to highways and national roads. The barriers are best suited for sections with few or no extreme curves. Also, where these barriers are installed on the median of two highways or lanes, there is the risk of accidents spilling over into the opposite lane because the posts give way to deflect the impact.

Thus, it’s essential to factor in the clearance space required behind the barrier. This is also true for installation to protect motorists from colliding with unforgiving objects. Enough clearance space is crucial to ensure the wire rope can stop the straying vehicle before it hits the rigid object.

What are the risks to road users?

Any type of barrier poses a risk for road users. The question is rather whether a collision with the barrier reduces the impact and is safer than colliding with the unforgiving object against which it protects.

Whenever there is the likelihood of a vehicle being able to return to the safety of the road or to come to a controlled stop without crashing, then it’s favourable not to have a barrier.

However, each type of barrier carries its own set of risks for road users. In isolated cases, the wire rope safety fence can give way too much and might be unable to stop a vehicle travelling at a high speed. The risk of vehicle body penetration upon impact is extremely low, making it safer in this regard than a steel-type barrier.

Why are wire rope safety fences not installed on kerbs?

The risk of roll and pitch occurring when a vehicle hits a kerb at a speed of, for instance, 70km per hour should be taken into account. The impact with the kerb can influence how the vehicle interacts with the safety fence. If a kerb is needed, the barrier offset must be at a sufficient distance after the kerb to enable the straying vehicle to regain control before it hits the barrier.

Alternatively, it must be installed close enough to the kerb that there isn’t sufficient time for roll or pitch to take place after the vehicle has hit the kerb. If a fence is installed on a kerb, the height of the ropes must be adjusted accordingly. Considering the importance of correct barrier placement, it becomes clear why expert installation is required.

Why is it important to ensure sufficient clearance between barriers?

Each road safety barrier type has its own characteristics and performance profile. Therefore, sufficient clearance between barriers is essential to allow for impact absorption, deflection and redirection performance.

What is the Safence?

It’s a road safety fence from Blue Systems, which Armco Superlite has developed along with Brdr. Markussens Metalvarefabrik (BMM). The barrier has been designed to meet the new European CEN standards and the requirements of NCHRP 350-TL3.

We install these barriers in accordance with strict requirements regarding clearance space, soil type, the distance between poles, and the tension required for the cables to meet the requirements of Blue Systems.

The fittings are made from grade 316 stainless steel, giving them optimal corrosion resistance and longevity. The rest of the steel components are galvanised to meet the requirements of SABS ISO 1462, also ensuring durability and resistance. View more information on the Safence barrier here.

Where to get more information and quotes on road safety fences in South Africa?

Reach out for more information on the Safence and other road safety products available from Armco Superlite in South Africa.