Components, systems and materials › Road furniture and safety › Crash cushion
Crash cushion
What it is
A crash cushion (impact attenuator) is a device placed in front of a fixed hazard that absorbs a vehicle's energy in a controlled way, bringing it to a stop or redirecting it.
Where it is used
Gore areas at exits, ends of concrete barriers, toll plaza islands, bridge piers near traffic and work zones.
How it works
Energy is absorbed by crushing cartridges, compressing elements or sliding panels, decelerating the vehicle over a set distance at survivable rates. Redirective cushions also guide side impacts back into the traffic lane.
Types
- Redirective and non-redirective cushions
- gating and non-gating designs
- sand-filled barrel arrays
- truck-mounted attenuators for work zones
Materials
Steel frames, crushable cartridges or plastic elements, sand barrels, anchors and transition panels.
Selection depends on design speed, hazard width, available length and required test level. The device must match the hazard's face with a crash-tested transition. Approach area should be flat so vehicles hit it at the designed height.
Installation and QA steps
- Prepare a level concrete pad.
- Anchor the unit as per the tested design.
- Fit the transition to the hazard.
- Add delineation.
- Inspect and reset or replace elements after each impact.
- Not reset after a hit, leaving no protection
- wrong test level for the speed
- sloping approach making vehicles ride over
- missing transition
Codes cited
- EN 1317 (series) (Europe): Road restraint systems: performance classes and impact test methods.
- AASHTO MASH (USA): Manual for Assessing Safety Hardware: crash test procedures for roadside hardware.
Cited by number only. We do not reproduce code text, tables or figures.
Related
Generic description for education. We do not name, endorse or compare manufacturers or products.
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