Truck mounted attenuators, also known as TMAs, are shock absorbing devices, that are attached to the back of large vehicles to protect workers and equipment. The purpose is to protect them from impact collisions.

In this article, we’ll discuss features and answer questions on these devices, including:

  • What are truck mounted attenuators?
  • What is the main function?
  • Why use these devices?
  • How do they work?
  • Advantages of using the equipment.
  • Factors to consider with installation.
  • Focus on Alpha 70K TMA™
  • Where to purchase these devices?
  • Why choose Armco Superlite?

What are truck mounted attenuators?

As already mentioned, these devices are designed to be attached to trucks. Specific sizes are available and should be selected based on the size of the vehicle and the impact energy it must absorb.

What is the main function of the device?

It functions to protect workers and equipment against the collision impact of vehicles. The heavy vehicle with the device attached to its rear is positioned behind the equipment and people it must protect from collision impact.

Why use truck mounted attenuators?

These devices are road safety improvement products. When workers are busy with road maintenance where vehicles usually travel at high speed, not even water-filled or sand-filled barriers can protect them from collision impact. They cannot perform their duties if they have to constantly worry about the risk of being hit by a speeding vehicle. Even if orange road cones or the temporary use of black and yellow delineators are placed to demarcate a lane around the workers and equipment, there is always the risk of a motorist losing control over their vehicle, ignoring the speed limit and warning signs, and ending up driving straight into the workers.

Apart from the loss of life as the result of the impact of a speeding vehicle, there is also expensive equipment that must be protected during the road maintenance project. A solid barrier is required to ensure safety. A truck provides an adequate barrier, but direct impact with it can cause it to move forward, and straight into the crew or equipment. The vehicle that directly collides with it, will probably be written off in the process while the occupants may suffer fatal injuries.

A truck with a visible sign to warn of slow-moving equipment or workers at site is thus not enough. It is also a hazard and increases risk for both workers and other road users. If attenuators are mounted to trucks, then a safety barrier is created as the collision is not directly with the truck.

How do these devices work?

The vehicle on which it is mounted, and which slowly moves behind the road maintenance crew is called a shadow vehicle. If the vehicle on which the device is mounted is stationary, it is called the barrier vehicle. In many instances, the shadow vehicle moves slowly behind the crew performing maintenance work on the road such as tarring, filling holes, levelling or painting of the road surface. If a crash occurs from behind the shadow or barrier vehicle, the attenuator acts as a crash cushion. The vehicle colliding with it comes to a stop.

Attenuators are designed to slow down the vehicle that collides with the mounted device. The devices also reduce impact force on the vehicle that collides with the cartridges.

The impacted device decelerates the vehicle that collides with it until the vehicle stops. The attenuator minimises impact damage to the barrier or shadow vehicle while it also protects the occupants of the barrier vehicle and those in the vehicle colliding with it.

Advantages of using truck mounted attenuators include:

  • Help to reduce the crash impact damage to the barrier or shadow truck.
  • Reduce the risk of direct collision impact with workers or expensive equipment.
  • Can be removed from the carrier vehicle and installed on another truck.
  • Reduced damage also means lower cost of repairs to the barrier or shadow vehicle.
  • Mobile way of protecting workers and equipment.
  • No need to deploy additional barriers.
  • Highly visible warning to motorists regarding road maintenance work in progress.
  • Help to save lives.

Factors to consider with installation

Keep in mind that these devices are tested and approved for applications on roads where vehicles travel at an average speed of 70 km per hour. It is essential to put up vehicle channelling devices, such as cones or delineators, in addition to early warning and slow-down signs to ensure the motorists are aware of the danger and reduce their speed appropriately.

Installation must be done strictly according to the manufacturer guidelines. Once an attenuator has been hit by a vehicle and has suffered damage, it must be inspected. Although replacement of the truck on which it is mounted may not be necessary, the performance of the attenuator can be compromised with a collision.

The TMA system must be assembled by persons who understand the assemble and deployment instructions and have experience in assembling road maintenance devices.

When used, the speed of travel and the skid distance must be taken into consideration when the barrier or shadow vehicle operates behind the work crew. The skid distance is shortened when a heavier vehicle is used while it is longer and more unpredictable when the barrier or shadow vehicle is lighter. For the Alpha 70K TMA™, the curb weight should be at least 6 800 kg with the required weight for the truck also being 6 800 kg to ensure the impact from behind doesn’t push the truck right into the crew or equipment it is meant to protect.

With skid distance in mind, the vehicle operator must leave enough open space between the truck and the work crew to minimise the risk of driving over them when hit from the rear.

Introduction to the Alpha 70K TMA™ attenuators

This TMA has been designed to meet the NCHRP 350 Test Level 2 criteria. It is designed for mounting on the back of a truck and because of its unique design, it is able to give exceptional protection to the driver, the road maintenance crew, equipment and motorists. It features a crushable aluminium body and is highly visible because of its familiar construction yellow colour.

Advantages of the Alpha 70K TMA attenuators include:

  • Impact protection for the barrier/shadow vehicle, occupants of the colliding vehicle and the crew which it must protect.
  • It is tested for protection against impact at 70 km per hour.
  • Designed to absorb the impact energy during a collision from the rear.
  • Mounted usage helps to reduce damage and risk of expensive road maintenance equipment.
  • It comes with the Durashell® Nose, which helps to protect against nuisance collision damage.
  • Corner damage is reduced with the tapered nose design.
  • The aluminium material used for the cartridge makes it lightweight and able to withstand corrosion and weather elements.
  • With the cartridge being lightweight, it is easier to assemble, install and transport.
  • The Durashell® Nose can recover its shape after a low-impact and low-speed collision, making it reusable after a nuisance collision.
  • The mounted attenuator cartridge is lowered by the driver from within the cab, using a hydraulic system.
  • When lowered and in place, the mounted cartridge prevents under riding of the truck by a passenger vehicle.

Where to purchase the Alpha 70K TMA™ mounted attenuators

It is best to buy these devices from local suppliers rather than attempting to import directly. The local supplier handles importation and adheres to the Consumer Protection Act regulations. The supplier is able to do good on their product and service promises. It is also quicker to get the mounted attenuators from a local South African supplier.

Why buy mounted attenuators from Armco Superlite in South Africa?

The firm has a national footprint with international connections. Each product supplied meets specific industry, performance and safety standards. With local offices, should repairs or replacement parts become necessary, the firm can perform, minimising the time it takes to get equipment up and running again. The company has a proven track record of road products supply throughout South Africa. It is possible to buy related devices, such as road cones, water-filled barriers, end-terminals, delineators and more directly from the same supplier.

Final thoughts on mounted attenuators

Loss of lives and equipment damage are imminent risks whenever road maintenance must be performed. Having the right equipment in place to create visibility and to protect the road users in addition to the work team and equipment is essential. The Alpha 70K TMA™ ranks as one of the most widely used and trusted truck mounted attenuators to provide the required protection. View more information on the Alpha 70K TMA ™ here.