Abstract:
The basic purpose for a truck-mounted attenuator (TMA) is to reduce the severity of impacts by errant vehicles into trucks being used in work zones. TMAs can be used on barrier vehicles, which are work vehicles that are stopped in a work zone to shield workers or equipment in front of the truck, or on shadow vehicles, which are work vehicles that are moving slowly behind other vehicles that are performing maintenance functions. NCHRP Report 230: "Recommended Procedures for the Safety Performance Evaluation of Highway Appurtenances," NCHRP 350: "Recommended Procedures for the Safety Performance Evaluation of Highway Features," and AASHTO’s "Manual for Assessing Safety Hardware" (MASH) have outlined specific testing requirements for TMAs. The United Kingdom has its own testing criteria for TMAs and the European Community is working on criteria for TMA testing that should be completed and implemented in 2013, if not before. TMAs are mandated in most states in the United States as well as the United Kingdom, Belgium, Netherlands, Norway, Sweden, Denmark, Australia, and New Zealand for selected work zone applications. TMAs are extremely effective when used to shield shadow vehicles, since few other options for protection are available. The "Manual on Uniform Traffic Control Devices" in the United States recommends, but does not require the use of TMAs.
