Protecting Workers on the Roadways: The Use of Truck-Mounted Attenuators in the Fire and Emergency Services

Workers who respond to roadway emergencies, such as vehicle crashes, can face multiple hazards. Working at roadway incidents frequently exposes responders to potentially being struck by passing motor vehicle traffic leading to serious injury or death. These secondary crashes during responses to roadway incidents contribute to about 50 emergency responder fatalities and injuries annually.[1][2] Additionally, crashes during roadway incident responses can cause extensive property damage to agency equipment, such as ambulances and fire apparatus.[3]

To protect their workers and expensive equipment during roadway incident responses, the emergency medical services (EMS) and fire service are beginning to adopt the use of truck-mounted attenuators (TMAs) that are commonly used in the construction sector. TMAs are energy-absorbing devices attached to the rear of trailers or trucks. They are designed to reduce the force of impact, thus reducing injury severity to the occupants of the vehicle crashing into the TMA and increasing survivability. Additionally, placing vehicles with TMAs before the roadway emergency, workers, or equipment, provides motorists an opportunity to change lanes, potentially avoiding rear-end-crashes.[4] As such, their use also reduces the risk of workers and equipment being struck.

Because of the increased use of TMAs in the fire and emergency services over the past five years, NIOSH’s Public Safety Program, Center for Motor Vehicle Safety, and Construction Program held a meeting with federal agency partners to discuss current knowledge about the use of TMAs by emergency responders and how best to inform proper use of TMAs at emergency response scenes. A summary of key messages from the meeting follows.

The History of the TMA

Historically, the use of TMAs has been limited to the construction and highway maintenance industries. In the 1950s, attenuators began as stationary items designed to absorb the impact of a crashing vehicle to improve occupant survival. Their success led to the creation of mobile systems, known as TMAs, in the early 1970s.[5] However, adoption and use of TMAs varied widely across states, prompting research into guidelines to standardize use. Resulting guidelines prioritized use where workers are exposed to moving traffic.[5]

Currently, a number of TMA designs are widely used in the construction industry. The Manual of Uniform Traffic Control Devices, specifically Part 6 – Temporary Traffic Control, provides several typical applications for TMAs. Additionally, multiple organizations have published guidelines for TMA design and use. A recent state-of-the-art review summarized factors impacting the safety of TMA deployments in construction[4]. Although TMAs were developed for use in construction, other industries such as public works are adopting the technology to protect their workers and equipment.

Use in the Fire and Emergency Services

Fire and emergency services, like construction, place a high emphasis on protecting their workers at emergency roadway incidents. When working on or along roadways, emergency responders are trained to place their apparatus in a blocking position to reduce the risk of injuries and fatalities from secondary crashes. This creates a large and heavy barrier between oncoming traffic and the work area where firefighters and EMS providers perform tasks. While this approach is effective at protecting workers, the vehicles used as blockers such as fire apparatus or ambulances, risk being damaged by oncoming traffic and distracted drivers.[3]

Damage to fire apparatus and ambulances can be very costly. Depending on the severity of damage, these vehicles may be out-of-service for a lengthy period to complete repairs. Loss of this equipment, for any length of time, can hamper a fire department or EMS agency’s ability to provide its primary services. Additionally, in recent years, both the price of and build-time for fire apparatus such as engines and ladder trucks have grown significantly. Current estimates place the cost of new vehicles without any tools or equipment at more than $1 million and they take between three to seven years to build before fire departments can place them in-service.

With these factors in mind along with inflation and limited budgets, fire departments and EMS agencies are actively looking for cost-saving opportunities while still protecting their personnel. This need is where the TMA entered the fire and emergency services.

Adopting the Use of TMAs

To date, fire and emergency services have begun adopting the use of TMAs as part of their operating procedures by:

• Working with and relying upon highway departments for deployment of their vehicles with TMAs to be used as blockers at roadway incidents;
• Repurposing reserve or retired apparatus or public works vehicles as blockers and retrofitting them with TMAs;
• Purchasing purpose-built blocker vehicles designed and equipped with TMAs; or
• Purchasing new apparatus with TMAs installed.

The primary use has been TMAs installed on current or retired apparatus to serve as blockers (Photo 1). This option allows fire and emergency services to provide protection to workers without the potential for a primary emergency response vehicle to become damaged and out-of-service.

Other departments have purchased a retrofitted apparatus with a TMA installed (Photo 2). To retrofit retired fire engines, the pump and compartment body are often replaced with a weighted plate for the chassis, an arrow-board, and storage for cones in addition to the TMA being placed on the rear of the vehicle. Modified vehicles can include fire engines, rescues, and ladder trucks.

Outside of repurposing and retrofitting, some departments have purchased purpose-built blocker vehicles outfitted with a TMA. A 2013 firefighter fatality investigation report discusses the use of these vehicles with TMAs. These vehicles are similar to those used in the construction and highway maintenance industries (Photo 3). Emergency lighting and radio equipment are added after acquisition. Other purpose-built blocker vehicles include those designed to block multiple lanes of traffic and deflect or redirect oncoming vehicles (Photo 4).

Before repurposing reserve or retired apparatus or purchasing purpose-built blocker vehicles, departments should consider any personnel constraints as these vehicles require additional personnel to operate them. Additionally, departments should consider consulting their fire apparatus manufacturers and vehicle insurance carriers prior to modifying a current or retired apparatus. To eliminate the need for additional personnel and potentially limit damage that would ordinarily cause a vehicle to be out-of-service, some departments are also purchasing new apparatus with a TMA installed.

Current Knowledge Gaps and Future Directions

Through years of trial and error from the construction and highway maintenance industries’ use of TMAs, the design of both the attenuator and mounting systems for the vehicle hosting the TMA has been carefully modified to ensure success. However, it is not clear whether this information has been effectively translated into the fire and emergency services’ use of TMAs, especially when a department chooses to retrofit a repurposed apparatus or add a TMA to an in-service apparatus. This raises several knowledge gaps including:

• Whether vehicles being equipped with TMAs are appropriate, in terms of design criteria, such as vehicle weight, center of gravity, and crash worthiness to adequately absorb crash impacts.
• Whether modified fleet vehicles are still performing their originally intended function and remain certified to their respective National Fire Protection Association (NFPA) standard (e.g., pump testing).
• Whether departments using TMAs complete National Traffic Incident Management Responder Training and receive specialized training on the proper use and deployment of TMAs. Specialized training may be developed by the department or agency, the TMA manufacturer, or other fire and emergency services representative organizations (e.g. Fire Department-Based Vehicles for Traffic Control).
• Whether departments train on proper use and deployment of TMAs on a reoccurring basis (i.e., drill nights or department exercise days). For example, the Grand Rapids Fire Department requires an initial 4-hour training course on their blocking vehicle with a TMA and a 2.5-hour refresher course every five years [6].
• How use of TMAs provided by highway or other agencies impacts local mutual aid agreements.
• Whether a designated method developed by a traffic incident management committee has been established to request a TMA equipped vehicle from a highway or other agency to respond to an event.
• An understanding of the types of incidents (e.g., crash or extrication-related) TMAs are typically dispatched for.

Moving forward, these gaps should be explored to ensure the safe and effective use of TMAs in the fire and emergency services. Additionally, NIOSH and federal agency partners identified the need for a national needs assessment for the use of TMAs by fire and emergency services. Results could lead to the development of specialized trainings, a selection and use document, or federal grant acquisition opportunities.

Share Your Department’s Efforts

If you are interested in adding to this conversation, please consider responding to the following questions in the comment section below:

1. If your fire department or EMS agency utilizes TMAs, do you have Standard Operating Procedures (SOPs) / Standard Operating Guidelines (SOGs) for their deployment and use? How do these procedures differ from the use of fire apparatus or ambulances in blocking positions?
2. What response conditions (e.g., type of roadway, speed limits, weather conditions, size of incident, type of incident) does your department or agency dispatch TMAs to the scene for?
3. What is your department’s main source of information about TMAs and their use?
4. Do you feel there is a lack of resources for the fire and emergency services on TMA use that federal agencies could address (e.g. training programs, deployment guidance, selection criteria, financial assistance programs)?
5. What were the key factors used in the decision-making process to purchase or modify equipment to include TMAs?
6. If your department does not use TMAs, has the department explored or pursued acquisition of TMAs?

Wesley R. Attwood, DrCJ, is a Public Health Advisor in the NIOSH National Personal Protective Technology Laboratory and Public Safety Program.

Meghan Kiederer, BA, is a Health Communication Specialist within the Research Branch of the NIOSH National Personal Protective Technology Laboratory and is the Communications Coordinator for the NORA Public Safety Sector Council and NIOSH Public Safety Sector Program.

David E. Fosbroke, BS, MSF, is a Research Statistician within the NIOSH Division of Safety Research and Partnership Liaison for the Center for Motor Vehicle Safety at NIOSH.

Tammy L. Schaeffer is a Safety & Occupational Health Specialist within the NIOSH Division of Safety Research and the Fire Fighter Fatality Investigation and Prevention Program.

Jarrad E. Clift, MBA, is an Emergency Medical Services Program Specialist with the National Fire and EMS Division within the United States Fire Administration.

Joseph Tebo is a Program Manager of the Traffic Incident Management Team in the Federal Highway Administration, Office of Operations.

David Bryson, EMT, is an Emergency Medical Services Specialist within the Office of Emergency Medical Services in the National Highway Traffic Safety Administration.

References

[1]         Federal Highway Administration [2023]. Secondary Crash Research: A Multistate Analysis. Washington, DC: Department of Transportation, Federal Highway Administration.

[2]         Responder Safety [no date]. Yearly Fatality Reports. The Emergency Responder Safety Institute, https://www.respondersafety.com/news/struck-by-incidents/yearly-fatality-reports/. Date accessed: July 18, 2024.

[3]         Nadeau R [2024]. Man charged with DUI after hitting Chesterfield fire truck, injuring himself and 3 others, including 2 firefighters. ABC 8 NEWS, https://www.wric.com/news/local-news/chesterfield-county/four-injured-including-two-firefighters-after-car-hits-chesterfield-fire-truck-shutting-down-i-95-for-hours/.

[4]         Aroke O et al. [2022]. Countermeasures to reduce truck-mounted attenuator (TMA) crashes: a state-of-the-art review. Future Transportation 2(2): 425-452.

[5]         Humphreys J, Sullivan T [1991]. Guidelines for use of truck-mounted attenuators in work zones. Transportation Research Record 1304: 292-302.

[6]         Corbitt-Dipierro C [2019]. Hardening Blocking Vehicles for Traffic Incidents and Planned Special Events: Report of Workshop Proceedings. Emergency Responder Safety Institute.