14-Point Checklist for Spec’ing Impact Attenuators
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Work zone intrusions are a fact of life, and utility fleets are turning to attenuators to protect employees.
One utility recently bought a truck-mounted attenuator vehicle from Royal Truck & Equipment after two of the utility’s employees were injured in an accident.
“Unfortunately, sometimes it takes an incident for people to realize they need protection for their work zones,” said Theresa Delgado, marketing manager for Royal Truck & Equipment (https://royaltruckandequipment.com), an attenuator dealer based in Coopersburg, Pennsylvania.
In a recent survey, 60% of highway contractors reported motor vehicle crashes in a work zone in 2020. As distracted driving incidents rise, even though overall traffic has been lower due to the pandemic, utilities are investing in attenuators to safeguard their employees.
An impact attenuator is a device designed to protect utility work crews in high-speed traffic locations and reduce the damage to vehicles or trailers by absorbing the colliding vehicle’s kinetic energy. The attenuator is placed in the oncoming traffic lane ahead of the work zone so a vehicle would be stopped before it could impact workers, equipment or hazards in the work zone.
Mobile impact attenuators come in two varieties: the truck-mounted attenuator (TMA) and the towable attenuator. The following checklist reviews some of the factors managers should consider when selecting attenuators to add to their fleets.
1. MASH certification. Attenuators must meet the minimum requirements of the Manual for Assessing Safety Hardware from the American Association of Highway and Transportation Officials.
2. Performance record. Ask how long the attenuator has been in the marketplace. Research how many crashes it’s been involved in and the results for the utility employees and the drivers.
3. MUTCD requirements. The Manual on Uniform Traffic Control Devices governs traffic control requirements for public roadways. Some states may have requirements in addition to the MUTCD. Fleet managers should follow guidelines for using TMAs in work zones.
4. Work profile. Attenuators are rated according to the speed limits on the roadways where they will be used to provide protection. A TL-3 device is rated for 62.5 mph, suitable for highway speeds. A TL-2 device is rated for up to 45 mph. San Clemente, California-based TrafFix Devices Inc. (www.traffixdevices.com) developed the TL-2 Plus TMA for speed limits up to 50 mph. “In many urban areas, utilities are exposed to 50-mph traffic, so this device reflects that reality,” said Jim Marshall, the company’s vice president of marketing.
Devices rated for lower speeds can be attached to smaller vehicles. TrafFix pioneered the TL-2 Plus rating with their Scorpion Metro device that’s 8 feet long, compared to the TL-3 option that’s 13 feet long.
5. Truck-mounted or towable. TMAs and towable attenuators must meet the same standards, so a TL-3 rating performs the same in either configuration. Towables provide flexibility and allow trucks to be freed up for other duties once the attenuator is in place.
6. Truck type. A TL-3 device may have to be installed on a medium-duty truck like a Freightliner or a Hino with counterweights that could reach 20,000 pounds gross vehicle weight. A TL-2 device can be attached to a lighter, less expensive truck – like a Ford F-550 – with a 7,500-pound curb weight. Utility managers have the flexibility to spec a TMA truck that fits their budget and the fleet’s needs.
7. Size. A TL-3 attenuator is around 13 feet long. The Scorpion line from TrafFix Devices hydraulically folds up and over the truck when not in use. In urban areas with narrow roads and alleys or areas with low clearances, the smaller TL-2 or TL-2 Plus option at 8 feet might be a better fit. It folds up at the rear but does not extend over the back of the truck bed, so it can fit in lower clearance situations and doesn’t take up as much space on the street.
8. New vs. retrofit. An upfitter like Royal Truck & Equipment can install an attenuator on a new cab and chassis, or a utility can deliver a new chassis for the upfit. Existing vehicles can be retrofitted as well. In any case, the truck must be fitted with the proper amount of ballast weight to reduce roll-ahead distance if the attenuator is struck, Delgado said.
9. Multipurpose use. Some states allow attenuator trucks to perform other duties, such as carrying plastic drums, cones and lane delineators. Some states do not allow anything to be carried in the bed of an attenuator truck because those items could become missiles in the case of an accident. Trucks can be outfitted with buckets for deploying traffic control equipment, barrel racks, sign cages and storage compartments.
10. CDL requirement. Most TMA vehicles don’t require a commercial driver’s license to operate them. However, some users specify equipment that may put a truck over the weight limit, so drivers must have the appropriate license in those cases.
11. One-touch deployment. Royal Truck & Equipment offers a system that deploys the attenuator and arrow boards with one touch to ensure all the safety measures are in use. That function improves safety and reduces liability risk, Delgado said.
12. Training. Work with a vendor that provides training or will train the trainer for the fleet and that offers videos and documents to ensure proper attenuator use.
13. Life cycle. The useful life of an attenuator could be five minutes or 15 years, depending on whether it’s involved in an accident, Marshall said. With proper maintenance, there’s really no limit to the life of an attenuator. Units that are involved in minor accidents can be repaired, recertified and returned to use.
14. Connectivity. Royal Truck & Equipment offers a connected arrow board kit that transmits work zone information to popular apps like Waze, Google and Apple maps. A connected hazard light kit performs the same function on trucks without an arrow board.
About the Author: Gary L. Wollenhaupt is a Phoenix-based freelance writer who covers the transportation, energy and technology sectors for a variety of publications and companies.