Most people have seen the huge trenches that look like sandpits on the side of highways in South Africa, sometimes with a truck stuck in them, but what are these areas? How do they work? Why are they there?
The facilities are called “arrester beds” and are a concept developed and implemented over time by transportation engineers and safety experts around the world. They’re a vitally important road safety tool, especially in mountainous or hilly areas where steep gradients are common.
According to Ryan Gaines, CEO of City Logistics (a privately-owned logistics company), these facilities can prevent catastrophic accidents that could result from trucks careering down steep slopes out of control.
“Take, for example, the arrester bed on Town Hill outside Pietermaritzburg. It has been used many times over the years and countless lives have been saved as a result. Road safety is a key focus at our company and we welcome this important tool.”
How does it work? The bed is filled with marble-like aggregate (commonly referred to as pea gravel or sand) or another energy absorbing material. The aggregate must have a high crush resistance. This is because when a heavy truck enters the arrester bed at high speed the material needs to quickly and effectively decelerate the vehicle to a stop. Aggregates with a high crush resistance can absorb and dissipate the kinetic energy of the truck more efficiently than aggregate with a low crush resistance.
There are many of these facilities spread across the country. Generally speaking, they are found where the risk of runaway heavy vehicles is high (for example on steep terrain, before tight bends and on approaches to toll plazas), where trucks might experience braking failure or other issues leading to loss of control. If this happens, the driver can steer the vehicle into the truck arrester bed. The loose material in the bed helps to gradually bring the vehicle to a stop safely and away from other traffic.
In South Africa, arrester beds are managed by the South African National Roads Agency. There’s no charge or penalty for using them (passenger cars can also use them. However, there is a charge for extracting the vehicle from the bed because it needs to be towed out. Responsible transport operators view this as a small price to pay given the many lives that can be saved.
What are arrester beds and how do they work?
Image: Arrive Alive
Most people have seen the huge trenches that look like sandpits on the side of highways in South Africa, sometimes with a truck stuck in them, but what are these areas? How do they work? Why are they there?
The facilities are called “arrester beds” and are a concept developed and implemented over time by transportation engineers and safety experts around the world. They’re a vitally important road safety tool, especially in mountainous or hilly areas where steep gradients are common.
According to Ryan Gaines, CEO of City Logistics (a privately-owned logistics company), these facilities can prevent catastrophic accidents that could result from trucks careering down steep slopes out of control.
“Take, for example, the arrester bed on Town Hill outside Pietermaritzburg. It has been used many times over the years and countless lives have been saved as a result. Road safety is a key focus at our company and we welcome this important tool.”
How does it work? The bed is filled with marble-like aggregate (commonly referred to as pea gravel or sand) or another energy absorbing material. The aggregate must have a high crush resistance. This is because when a heavy truck enters the arrester bed at high speed the material needs to quickly and effectively decelerate the vehicle to a stop. Aggregates with a high crush resistance can absorb and dissipate the kinetic energy of the truck more efficiently than aggregate with a low crush resistance.
There are many of these facilities spread across the country. Generally speaking, they are found where the risk of runaway heavy vehicles is high (for example on steep terrain, before tight bends and on approaches to toll plazas), where trucks might experience braking failure or other issues leading to loss of control. If this happens, the driver can steer the vehicle into the truck arrester bed. The loose material in the bed helps to gradually bring the vehicle to a stop safely and away from other traffic.
In South Africa, arrester beds are managed by the South African National Roads Agency. There’s no charge or penalty for using them (passenger cars can also use them. However, there is a charge for extracting the vehicle from the bed because it needs to be towed out. Responsible transport operators view this as a small price to pay given the many lives that can be saved.
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