Prevention through Design

Origins and Growth:

Although the need for Prevention through Design (PtD) was suggested in the NSC’s 1955 Accident Prevention Manual, application of PtD in the U.S. construction industry did not occur until the Construction Industry Institute-sponsored research by Professors Jimmie Hinze and John Gambatese in the 1990s. The PtD concept has been slowly recognized and applied in the U.S. over the past twenty years. PtD-related publications and industry interest increased dramatically after a 2003 symposium held at the University of Oregon (Hecker et al 2004). Large design-builders such as URS, Parsons and Jacobs Engineering have established PtD programs and Kiewit, Fluor, Mustang Engineering and Zachry Engineering have taken steps towards implementing a PtD program. Large owners who have implemented PtD on at least one project include Intel, the Southern Company and ExxonMobil. Representatives from the U.S. Department of Energy and the U.S. Army Corps of Engineers have also expressed interest in developing a PtD program. OSHA has convened a Design for Construction Safety workgroup composed of approximately ten professional organizations since 2005. The National Institute for Occupational Safety and Health (NIOSH) has recognized PtD as a highly promising safety approach. In 2006, PtD became of one of ten focus areas of the National Occupational Research Agenda (NORA) Construction Sector Council. In 2007 and 2011, NIOSH convened PtD workshops with several hundred participants from eight industry sectors. An ANSI PtD standard has been published and an ANSI PtD technical report is forthcoming. The US Green Building Council’s current LEED sustainability rating system now includes a pilot credit for PtD.

 

Future of PtD:

A classical problem in physics is to calculate the trajectory of a moving body, such as a projectile fired from a cannon. If one knows the initial velocity and direction of the projectile and environmental variables such as wind, one can calculate where the projectile will be at any point along its path. The concept of trajectories can also be applied to gain insights into how CHPtD may evolve. In a 2008 article published in the Journal of Safety Science, Toole and Gambatese suggested that CHPtD is likely to follow four specific trajectories:

1. Increased prefabrication. Prefabrication involves the assembly of pieces in temporary locations, such as specialized manufacturing facilities, followed by the transportation of the assembled components to their permanent location and the final fit up to create the completed facility. Prefabrication may reduce the hazard level of a task in two ways. First, the location of the work can be shifted to a lower hazard environment, such as from a high elevation to the ground, from inside an excavation to where there is no risk of soil cave-in, and from inside a confined space to an open space where there is less risk of hazardous air quality. Second, prefabrication allows work to be shifted from the field to a factory, which allows the use of safer, automated equipment in improved environments.

 

2. Increased use of less hazardous materials and systems. Design professionals typically specify materials based on perceived or experienced performance and cost, rarely on the inherent safety of the materials for construction or maintenance workers. Progressive owners and designers are becoming increasingly aware that some materials offer essentially similar performance and cost as that of competitive products, yet are considerably less hazardous to install or apply. This is particularly true for coatings, adhesives and cleaners, which are associated with air quality, flammability and skin hazards.  As information technology makes it easier for designers to obtain information about the inherent hazard level of various building materials, designers will increasingly be expected to apply this information in their design decisions.

 

3. Increased application of construction engineering. There are many instances when engineering is required to plan or execute a construction task. Soil retention systems, crane lifts, soil bearing analysis for supporting construction equipment, temporary structures, fall protection anchorage points, and temporary load analysis are all examples of construction tasks that require the application of engineering principles because they involve forces and stresses. Traditionally, contractors have been required to provide these construction engineering tasks through in-house employees or consultants. Progressive owners are now realizing that when design engineers perform no engineering related to the construction process, important construction engineering tasks may be performed by unqualified personnel or not performed at all. Also relevant is the fact that the growth of design-build has led to an increase in construction engineering capability among designers who previously been less involved during the construction stage of their projects.

 

4. Increased spatial investigation and consideration. The growth of both CHPtD and design-build may cause designers to begin communicating potential site hazards to the constructor on drawings and other project documents. In addition, design engineers may be expected to incorporate into their designs at least a crude understanding of necessary working distances for each of the various construction trades and common tools. Examples include the minimum legal proximity for cranes to powerlines, the minimum trench width necessary to allow efficient pipe placement and connections, the minimum spacing between electrical raceways and adjacent structures to allow safe and efficient installation, and the minimum clearance between steel bolts and adjacent steel members to allow the use of typical positioning and bolting tools or field welding. Spatial considerations for constructability may also include ergonomic issues. For example, the design of structural steel, plumbing, HVAC and electrical systems will include consideration of whether connections requires the worker to work over his or her head or at an awkward angle that is more likely to result in musculoskeletal injuries.