What are the best practices for selecting and installing crash cushions on highways?

1 Types of crash cushions

Different types of crash cushions are available, depending on the performance, maintenance, and cost requirements. Sand-filled barrels or attenuators are the most common type and consist of a series of plastic drums filled with sand and arranged in a tapered configuration. Although they are easy to install and repair, they may not be ideal for high-speed or high-volume roads, as they can scatter sand and debris on the pavement. Hydraulic or mechanical attenuators use metal or plastic components that deform or slide under impact to dissipate the kinetic energy of the vehicle. They are more durable and effective than sand-filled barrels, but require more space and regular inspection. Energy-absorbing foam or honeycomb systems use a core material that crushes or compresses when hit by a vehicle to absorb the impact force. These systems are compact and lightweight, but may be more expensive and difficult to replace.

2 Selection criteria

When selecting the appropriate type and size of crash cushion, several factors should be taken into consideration, such as the design speed and traffic volume of the road, the width and alignment of the road, the type and size of the target hazard, and the environmental and climatic conditions. These factors will determine the frequency and severity of crashes, the need for quick restoration of service, the level of protection and containment needed, as well as the performance and durability of the crash cushion materials.

3 Installation guidelines

The installation of crash cushions should adhere to the recommendations and specifications of the manufacturer, as well as the relevant standards and regulations of the highway authority. Generally, it should be located close to the target hazard, with sufficient clearance for maintenance and emergency access. It should also be aligned with the direction of traffic and the target hazard, without any gaps or offsets that could cause snagging or deflection of the vehicle. Additionally, it must be anchored securely to the pavement or foundation using appropriate fasteners and anchors. Finally, it should be marked and signed clearly with reflective materials and warning signs in order to improve its visibility and recognition by drivers.

4 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?