Vehicles travel at high speed on highways. Though the vehicles move in the same direction, the risk of serious accidents is a reality. Highway barriers are installed specifically to improve the safety profiles of highways. However, certain types of barriers work better for specific situations than others.
The Type of Barrier Installed is Dependent on Factors Such As:
- Length of the section where the safety barrier must be installed
- Whether the barrier must be installed in the median or on the side of the highway.
- The speed of travel on the particular road
- The space available as certain types of barriers take up more road surface space than others
- Obstacles and potential hazards such as water sources against which protection must be in place
- The clearance height of the vehicles that use the road
- The redirection required; and
- Main purpose of installation.
If the rail is to be installed along the entire length of a particularly long section, then it is imperative that it be durable. Any damage it suffers as the result of a vehicle colliding with it, must be repaired. The question is whether the entire system is affected or only a portion. Any road maintenance on a highway carries risks for the workers, equipment, and highway users. It must thus be possible to repair the damage quickly to minimise risk for the highway users and workers.
Cost-effectiveness is also a consideration when it comes to long stretches where such barriers must be installed. If the barrier is too expensive to install and maintain, it cannot be used for long stretches of road. The heavier a barrier type, the more expensive it is to transport and install.
Armco Superlite guardrails have an array of benefits including warning drivers of potential danger, reducing centreline crowding, restraining wayward vehicles, and retaining high visibility at night. However, before choosing the best barrier, a few considerations should be made.
Location of the Barrier
Placement of a barrier in the median is normally for the following reasons:
- To prevent vehicles moving in an opposite-flowing direction from making U-turns over the median into the fast-moving traffic from the opposite direction
- To prevent accidents from one highway spilling over to the opposite-flowing highway
- To help reduce the glare effect from the lights of vehicles moving in the opposite direction; and
- To redirect straying vehicles back into their lanes upon side-collision at an angle with the road barrier.
If enough space is available between two opposite-flowing highways, it is possible to plant shrubs on a grass island between the highways. This helps to prevent glare from lights, reduces the risk of vehicles moving into the opposite-direction highway, and provides sufficient space between the highways. This can prevent accidents which might result from one highway spilling over to the other.
Installation of the W-beam guardrail system on such grass islands, along with shrubs, improves the safety profile even more. These guardrails cannot be penetrated and thus provide superb stop power to prevent motorists from breaking the law through actions such as U-turns. Installation of these barriers thus helps to improve road safety.
Different Types of Guardrail Barriers
With expansion space often not available, urban planners have to think of ways to add more lanes to highways without using more horizontal space. In order to do so, they have to reduce the space that the barriers take up, including the median barriers. To this end, they have options such as concrete and wire-rope barriers and W-beam guardrails. Let’s look at these options in greater detail.
- Wire-rope barriers: These have the smallest horizontal footprint. They are effective in preventing breakthrough on side-impact. The cost of repair is reasonable and repairs can be done quickly. However, a large section can be removed with one collision. This means the barrier must be repaired immediately to ensure ongoing safety on the highway.
- Concrete barriers: These are often placed in the median area between two opposite-direction highways where there is no longer space to expand, but additional lanes are needed. They are highly effective in preventing vehicle accidents from spilling over to the opposite-direction highways as they are extremely rigid. However, this means that the vehicle and its occupants take all the impact energy upon collision with the concrete. On a side-angle hit, the vehicle can move back to its lane because of the slight slope at the bottom of the barrier. The friction between the vehicle and concrete helps to slow the vehicle movement. Apart from being rather unforgiving, these barriers are heavy. Special equipment is needed for installation. Nonetheless, these barriers don’t require regular maintenance, and damage to one section doesn’t affect the integrity of another section on the same stretch of road.
- W-beam guardrails: This barrier solution is made from galvanised steel panels that are attached to sturdy posts. These posts are planted into the soil. Where the guardrails are used as median barriers, the panels are attached to both sides of the posts. The entire system works to absorb and distribute impact energy from a collision, thereby reducing the force of impact on the vehicle and its occupants. W-beam guardrails are effective in preventing a breakthrough to the opposite-direction highway and to hazards behind the guardrails. Due to the design and working of these barriers, a clearance space is required behind the barriers. As such, these barriers require more horizontal surface space than the wire-rope safety fences and concrete barriers.
What Makes W-Beam Guardrail Barriers so Effective?
As mentioned earlier, these barriers work as entire systems. When a vehicle collides with the steel barrier, the entire system takes the force of the collision. This makes the system strong and helps to prevent a breakthrough. To prevent vehicles from going over the guardrails, these barriers are installed at the appropriate height to cater for the speed of travel and the vehicle ground clearance. Since they are made from steel and posts, these barriers can also give way to a certain extent. This helps to absorb impact energy.
The W-beam design makes the steel extra strong. In addition, the steel is galvanised to protect it from weather elements that can cause it to rust and thus lose integrity. Where non-galvanised steel is used, coats of protective paint are applied to protect the underlying steel against corrosion.
Apart from being used as barriers on highways, W-beam guardrails are also installed on bridges, mountain passes, in urban areas to prevent vehicles from moving onto pavements, and to prevent straying vehicles from going into hazardous areas such as water sources, ditches, and down slopes. These barriers also prevent straying vehicles from hitting unforgiving obstacles such as street poles, signage boards, walls, cliffs, buildings, and trees.
The W-beam guardrails, much like any other barriers, are obstacles as well. This means that when hitting one of the barriers, some level of damage to the vehicle can be expected. As such, the risk of serious damage and injury because of the barrier must be weighed up against the risk should there not be a barrier in place. With that in mind, road engineers consider factors such as:
- Type of obstacle against which it must protect
- Clearance distance behind the barrier
- Speed of travel
- The distance from the safe travel path to the hazard
- The damage and injury that can be expected should the barrier not be in place; and
- Surface availability.
If enough clearance space is available for a straying vehicle to allow for corrections and safe return to the travel path without excessive risk to other road users, then it might be better to not to install a barrier. However, in most instances where such barriers are installed, the risk of serious injury and fatality is too high without a barrier in place. With W-beam guardrails, concrete barriers, and wire-rope fences installed on highways and other roads, motorists gain more confidence to drive in their allocated spaces.
With the high speed of travel allowed on highways, it is unsafe to have two adjacent and opposite-flowing highways without appropriate barriers in place. Though the presence of these barriers cannot guarantee that there will be no fatalities, they serve an important role by helping to prevent accidents, reducing the force of impact, and reducing the severity of accidents on highways.
Correct installation of these barriers is essential in addition to the correct choice of barrier and the use of quality materials. Working with a trusted supplier of road-safety products is thus essential to ensure that the safest possible option is selected. Armco Superlite is a well-established supplier of such road-safety barriers in South Africa. Get in touch with us for more information about our W-beam guardrails and wire-rope safety barriers.