The purposes of this section are to provide quick access to basic information about attenuators used by Caltrans and to allow quick, rough comparisons of different kinds of attenuators in support of Work Zone planning. To access available information and make comparisons among various devices, please use the Information, Compare, and Sort links in the navigation area to the left of this page.
The primary sources of this information are NCHRP 350 approval letters.
The next steps in developing these pages are to improve the information presented and to review the presentation format. This will require practitioner input.
Following is a statement of basic assumptions about attenuators used in developing these pages. The source of this information has been derived from other states. This information is believed to be appropriate for use in California, but it will almost certainly need modifications and/or clarifications both for accuracy and to reflect practitioner perspectives.
Basic Definition of an Attenuator
Attenuator — An impact attenuator directly absorbs the energy of an impacting vehicle and reduces the force on a vehicle occupant to an acceptable level.
Basic Types of Attenuators
Truck-Mounted Attenuator (TMA) — Truck-mounted attenuators are safety devices used for mobile operations conducted near traffic. They are energy-absorbing devices attached to the rear of the trucks used as protective vehicles, thus protecting the motorist and the protective vehicle's driver upon impact. Some kinds of attenuators, such as Scorpions, also work by redirecting errant vehicles, although this is a secondary effect. Attenuators are used with warning signs, revolving lights, and flashing arrow panels.
Fixed Attentuators — The most common type of stationary attenuator are sand-filled barrels, although there also many kinds of proprietary crash cushions that are used when there is not enough width for sand barrels. Sand barrels are configured in increasing weights from the impact point toward the object. Such an array transfers the vehicle's momentum to the increasing masses of sand in the barrels and provides a gradual deceleration. Sand barrels are often used as crash cushions for concrete traffic barriers and to shield fixed objects that cannot be removed or relocated. Sand barrels can be used for temporary protection of in work zones.