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Thomas G. Bobick, Ph.D., P.E., CSP, CPE, a research safety engineer with NIOSH, is project officer for an applied research effort that has developed a fall prevention system applicable to sloped and flat surfaces in the residential, commercial, and industrial construction industries. In this interview, Bobick explains how he and his research team developed this system and provides an update on the status of other current NIOSH safety-related research projects.

As part of NIOSH’s National Occupational Research Agenda (NORA) Construction Sector long-term goals, you and your colleagues have designed an adjustable roof bracket-safety rail system to protect workers from falls. How did you and your colleagues arrive at the design for this system? What kind of industry research did you conduct prior to creating a prototype?

Analyses of Bureau of Labor Statistics (BLS) data consistently indicate that falls from elevations are the leading cause of fatality in construction. In addition, analysis of nonfatal BLS data showed that excessive days away from work are caused by falls through roof and floor holes and through skylight fixtures. BLS data analyses for 1998-2005 indicated that a yearly average of 154 workers were killed and 3,374 workers were severely injured in construction due to falling from roof edges or through roof holes and skylights. In an attempt to address the fall-from-elevation problem in construction, we evaluated the strength of two commercial guardrail systems and compared them with the strength of job-built guardrails.

During this testing, the research team developed the concept and a prototype for a fall prevention system that combined an adjustable roof bracket with a self-contained guardrail system that can be used on residential, commercial, or industrial construction sites for guarding unprotected roofs, floor openings, stairwells, balconies, and decks. The research team consists of Tony McKenzie, Ph.D., P.E., a research safety engineer, Doug Cantis, a physical science technician, Dave Edgell, an instrument maker/machinist and myself as project officer.

The initial prototype was based on the design of a typical roof scaffold bracket that is used to support a worker or roofing supplies on a residential roof during typical roof construction. However, a pocket has been attached to the back end of the bracket that accepts a 1-in square, 6-ft long metal tube that is bent at one end. Slid onto each tube are 3 metal supports that are hand-tightened and can be adjusted to the correct heights for the top rail, mid-rail, and toe board that are required for an OSHA-compliant guardrail system.

Our extensive laboratory testing of this system included an evaluation of OSHA’s requirement to support 200 lbs in an outward and downward direction at any point along the top rail of the system. The guardrail system was attached to a small-scale roof (12-ft wide and 10-ft upslope) that could be adjusted to any roof pitch desired. This roof setup was developed for use in the DSR High Bay Lab. For our testing, it was required that three 16-penny nails (3½” length) be used to fasten each bracket to the roof test setup.

A humanoid manikin was supported on a metal structure (total weight 225 lbs) that was attached to the roof test setup. A calibrated force gauge (load cell) was used to measure the load, which was applied when the manikin fell against the top rail. We designed the bracket portion that attaches to the roof to be adjustable through 7 different roof pitches, from 6/12 (27°), 8/12 (34°), 10/12 (40°), 12/12 (45°) to 15/12 (51°), 18/12 (56°) and 24/12 (63°). The bracket can also be adjusted for installation on flat surfaces.

In addition to the OSHA 200-lb top rail requirement, the design team developed a unique test method that uses a hydraulically powered system to pull all configurations to failure. This pull-to-failure test involved pulling simultaneously on both the top and mid-rails until either the system pulled apart, pulled free from the roof, or survived with the hydraulic system stalling at the maximum output of 800 lbs loading.

The final design that was tested successfully supported a drop of 430 lbs to the top rail, more than twice the OSHA top-rail requirement. Additionally, the system successfully stayed intact and stayed attached to the roof during a pull-to-failure test of 525 lbs.

Many fall protection products apply only to flat surfaces, adjust for only a few roof pitches, or lack components to support a horizontal guardrail. However, the NIOSH adjustable roof bracket-safety rail system, as mentioned above, can adjust to seven roof pitches (from 27º to 63º). It can prevent workers from sliding off roof edges, falling through unprotected roof/floor holes and existing skylights, falling into stairwells, and falling from unguarded balconies or decks.

What other features are unique to the NIOSH system?

The most innovative feature of the system, and for which a patent has been applied, is the adjustability of the brackets that support the top rail and the mid-rail. Other commercially available guardrails have the cross-rail supports welded in place. As the upright post tilts backward because of the increase in roof pitch, the vertical height of the top rail above the scaffold plank (the walking-working surface) decreases with increasing roof angle. Measurements have indicated that the vertical height of the top and mid-rails can decrease below the specifications of the Fall Protection Standard (Subpart M) of the OSH Act. In addition, the NIOSH guardrail system has been designed to keep the walking-working surface level at all of the roof pitches to which it can be adjusted. The design of the bracket-rail system uses a toe board along the walking surface to prevent a worker’s foot from slipping off the plank while focusing on the work in front of them. The bracket design also uses a slide guard underneath the plank surface to prevent any objects that might be dropped from sliding off the roof and striking anyone on a lower level.

During January 2009, the design team was informed that all 42 claims itemized in the patent application were allowed by the U.S. Patent and Trademark Office and that the patent would be issued within two to four months. This is great news.

You have exhibited the adjustable roof bracket-safety rail system during 2008 at a construction meeting and at ASSE’s professional development conference. How have fall protection manufacturers and those in the construction industry responded to the system thus far?

We received a great deal of favorable interest at both the ASSE professional development conference and the 2008 Construction Safety Conference held in Chicago (Photo 1). Because of exposure at both shows, different segments of the construction industry have provided encouraging feedback. Both general contractors and roofing subcontractors have inquired as to whether the system is commercially available. Many construction workers have indicated they would use the system if it were on the jobsite.

Most encouraging was feedback received from representatives of two insurance companies. One individual commented that a contractor’s insurance premiums would probably be reduced if this system would be regularly used on the jobsite since it was a system that prevented the fall from occurring in the first place, not just protecting a worker after the fall had occurred.

Have any manufacturers agreed to produce the adjustable roof bracket-safety rail system? When do you expect the system to be on the market?

A few companies that market fall protection products have indicated their interest, and we assisted them with installing the system on different worksites to provide them hands-on experience (Photo 2). None of the companies have yet made the commitment to enter into a partnership with NIOSH to bring this system to market. Recently, a metal products fabricator located in West Virginia has indicated possible interest to fabricate the components and to make the system available through their website. To fill in for their lack of specific marketing for this product, NIOSH is developing a brochure, a booklet, and a companion DVD that will discuss the safety features of the system and provide instructions to install the system at hazardous areas in residential, commercial, and industrial construction sites. For a copy of the brochure, please contact me at tbobick@cdc.gov.

We are having productive discussions with a potential partner. Until a licensing agreement is signed to formally establish the partnership, it is difficult to estimate when the guardrail system will be commercially available.

Are you and your colleagues researching or developing any other fall protection systems?

In addition to the roof assembly, the design team has developed a similar system with a smaller 6-in by 6-in footprint that can be used in flat work areas with restricted space, such as stair treads. This smaller version will use a shorter length of vertical pole but will still use the adjustable braces that support the top rail and mid-rail.

I also had an opportunity to attend and take part in a meeting with the Fall Protection Work Group of the OSHA Advisory Committee for Construction Safety and Health and learned of a specific fall protection need related to unfinished stairs. Currently, many companies require workers to wear a personal fall arrest system (safety harness) and to be properly tied-off. This can easily create a tripping hazard if the worker must repeatedly walk up and down steps while tied-off. Installing perimeter guarding to the stair tread is not always an option if the construction specifications prohibit this. Because of this identified need, the research team developed a vertical fixture that can be used on the surface below the stairs that will accommodate the vertical pole and the adjustable supports for the mid-rail and top rail, which will provide the required handrail protection. This vertical fixture has been demonstrated in the field, and the crew supervisor commented favorably about wanting to use this vertical assembly.

Other researchers with the Division of Safety Research in Morgantown, WV have ongoing projects that focus on different aspects of working at elevations. These projects include:

  • an attachment to the personal fall arrest system to elevate the legs of a fallen worker to prevent suspension trauma;
  • an analysis of the fit of the personal fall arrest harness to provide better-fitting harnesses to prevent trauma if a fall occurs;
  • development of an attachment for extension ladders to provide a visual, auditory, and vibratory signal for correct angle setup;
  • analyses and computer modeling of a scissors lift for stability indications when individuals work with the lift fully extended;
  • a pilot project that will evaluate whether a properly supported wood-frame structure in residential construction, such as a roof truss, can be used as an anchorage location for a fall arrest harness. Information on these other projects can be obtained from the branch chief, Hongwei Hsiao, Ph.D., (304) 285-5910, hhsiao@cdc.gov.

NIOSH has also developed a wearable electrical field sensor that alerts workers when they are too close to an electrical field. What is the status of this device, and how does NIOSH predict the device will reduce injuries and fatalities from electric shock?

NIOSH has developed a prototype of the electric field sensor to detect the human proximity and electrical contact to a 120-volt live circuit, and the human proximity to a 9,000-volt live power circuit. Results from laboratory tests indicated that it is feasible for the electric field sensor to detect human proximity and contact with live circuits.

Researchers speculate that as workers wear an electric field sensor on their wrist and receive an audible and visual warning when they are close to an unexpected live circuit, many electrical injury incidents may be avoided.

According to occupational electrocution fatality data, about half of electrocution victims touched an overhead live circuit. If the victims had worn an electric field sensor, they could have received a warning and could have avoided the electrocution. Many of the overhead-circuit touching victims were electrocuted through a metal ladder or conductive tool they carried. Further research should be conducted to explore whether the sensor could be effective when a worker holds a conductive tool and approaches a live circuit.

Has NIOSH also exhibited the electrical field sensor to those in the construction industry? If so, how did they respond?

NIOSH posted this project concept on the Federal Business Opportunities website (http://www.fbo.gov) to seek an industrial manufacturer for future collaboration. To date, no construction safety equipment manufacturers or other companies have contacted NIOSH for any information about the concept. Information regarding this sensor can be obtained from Shengke Zeng, Ph.D., (304) 285-6103, szeng@cdc.gov.

What are the Division of Safety Research’s plans for 2009, and how do they align with NIOSH’s strategic and intermediate goals?

The Division of Safety Research is the lead for the Traumatic Injury (TI) research program. The TI program recently underwent a National Academies review of the relevance and importance of research activities over the past 15 years. The report outlining the National Academies’ recommendations was received in August 2008 and can be viewed at: http://www.cdc.gov/niosh/nas/traumainj/pdfs/NA-TI-report-August2008.pdf.

The TI program is currently developing a plan to implement the recommendations for future research activities. Specific goals of the program are still being finalized, but the 6 primary areas of the TI program are to reduce occupational injuries and deaths from:

  • falls;
  • workplace violence;
  • machines and industrial vehicles; and
  • among high-risk and vulnerable worker groups; and
  • increase the use of surveillance data to guide research and prevention efforts.

These 6 primary areas drive NIOSH’s research planning for the TI program. The Division of Safety Research has individual projects in each of these 6 primary areas. For an overview of the TI program, visit http://www.cdc.gov/niosh/injury.


Thomas G. Bobick, Ph.D., P.E., CSP, CPE, a research safety engineer with NIOSH, is project officer for an applied research effort that has developed a fall prevention system applicable to sloped and flat surfaces in the residential, commercial and industrial construction industries. Bobick has worked for the federal government for 39 years. His entire career has focused on workplace health and safety.

In 1970, he received a Bachelor of Science degree in mining engineering from Penn State University and subsequently worked for the Bureau of Mines (Department of the Interior) in Pittsburgh, PA for 19 years. He conducted a wide variety of research activities for the coal, metal, and nonmetal mining industries, both underground and at surface operations. These activities included methane gas control, extensive noise and vibration control, and topics related to human factors research, including back and upper extremity injury prevention, task analysis and workplace redesign, and assessment and control of whole-body vibration from surface and underground mining equipment. While working for the Bureau of Mines, he received a Master of Science degree in industrial hygiene from the University of Pittsburgh in 1988.

In 1989, Bobick transferred to NIOSH, Division of Safety Research (DSR) in Morgantown, WV. He was involved in ergonomics research for agriculture and fall prevention research for construction from 1989 to 1995. In 1995, he was selected to be part of the long-term training program to return to school for advanced training in research methodology. In 1997, he received a Doctorate in industrial engineering with a specialty in ergonomics from West Virginia University.

After returning to work with DSR, he was involved with two laboratory evaluations of back-support belts. Following those studies, he worked again in fall prevention research for the construction industry. As part of this work, he serves as the DSR representative to the Construction Sector Council of NIOSH’s NORA and is co-chair of the NORA Work Group focused on TI events (falls, electrocutions, struck-by, and caught-between). This work group will develop and guide implementation of the traumatic events goals found here.