The construction industry remains one of the most hazardous industries in the United States in terms of the number of occupational fatal and non-fatal injuries. In 2014, 874 fatal work-related injuries were reported in the U.S. construction industry1. Even though construction workers historically account for only about 5% of the overall U.S. workforce, the construction industry accounts for approximately 20% of the total occupational fatal and non-fatal injuries2.
Numerous studies have indicated that the high incident rate in construction can be influenced by the design of projects. For example, 42% of 224 fatalities in the U.S. construction industry between 1990 and 2003 were linked to decisions made during design, before the start of construction3.
To curb the high number of fatal and non-fatal injuries, safety management strategies are emphasized by construction stakeholders. Firstly, safety management involves preparing a plan to ensure that all safety hazards and risks are identified, assessed, analyzed, and then mitigated. This step is aligned with lean thinking where design and construction processes are streamlined to eliminate waste and maximize value.
Workplace accidents can have negative impacts on cost, schedule, and quality. Therefore, it can be argued that improving workplace safety is a form of waste reduction and value generation. According to the “hierarchy of controls” (HoC), eliminating construction hazards at the source is the most effective means of improving occupational safety4, as shown in Figure 1. HoC, in this regard, is defined as a means of determining how to implement the most practicable and effective safety controls on the jobsite to control safety hazards4.
By examining the graphical pyramid (Figure 1), consistency between lean thinking and safety management principles appears evident. However, eliminating safety hazards at the source, a.k.a., Prevention through Design (PtD), requires modifying the facility design prior to construction operations. It is worth noting that PtD encompasses the concept of protecting construction workers by addressing their safety during the design process5. In that aspect, lean design practices appear on the surface to touch on this critical subject because they promote the early involvement of specialty contractors and frequent team communications between project teams, particularly between design and building professionals.
Figure 1: Hierarchy of Controls4
Numerous lean design practices can be implemented to prevent safety hazards, and hence improve construction site safety. An apparent alignment between lean design principles and the concept of PtD has been reported6. For instance, the concept of set-based design (SBD), which entails generating different design alternatives up-front and deferring detailed specifications until optimal trade-offs are completely understood and until the last responsible moment, can be used to create different safety design solutions for a facility.
Using cross functional teams (CFTs) helps to generate a broader set of design alternatives that are free of waste/hazards because each of the team members bring different perspectives to the design. Superior outcomes in terms of the physical design of a facility can emerge when lean design practices such as SBD, CFTs etc are integrated into the design process. However, narrowing down the set of design alternatives to one optimal design is a challenging task. The Choosing By Advantages (CBA) decision-making system, another lean thinking tool, is recommended to address this challenge7. CBA is a collaborative and transparent lean application method used to make sound decision-making by basing decisions on the importance of advantages between alternatives. The application of CBA within the AEC industry has been discussed in the literature. For more details about CBA, readers are encouraged to review the CBA blogs on this website.
With regards to the application of lean practices for making safety decisions, CBA was employed to select an optimal design to protect construction and maintenance personnel on the rooftop of a one-story physical utility building on a medical facilities campus in Portland, Oregon7. The decision-makers initially considered three fall-prevention measures for this particular case study.
The first alternative involved installing a temporary guardrail system on the building rooftop that meets federal and state safety requirements. This option is considered an engineering control, according to the HoC. The second alternative was to specify a permanent roof anchor system to provide workers with tie-off points. This solution is considered a combination of both administrative and engineering controls. The third and last alternative was the incorporation of a PtD solution, represented by modifying the facility design to include a tall parapet around the perimeter of the roof. The inclusion of a tall roof parapet eliminates the need to install fall protection measures by providing permanent protection around the entire rooftop perimeter and throughout the facility’s life-cycle.
One advantage of this alternative over the other two alternatives is that this design modification eliminates the risk of falling over the sides of the roof during construction and maintenance operations. This advantage was considered by the decision-makers as the most important advantage in terms of generating value to construction stakeholders. Based on that, the PtD solution (alternative #3) was found to generate the greatest value to construction stakeholders and, therefore, was selected at the end of the CBA process as the best design alternative for this particular case study. Table 1 summarizes the CBA results of this case study.
Table 1: CBA Analysis to Select Optimal Fall Prevention Measure 7
To recap, this blog examined the impact of lean design practices on improving safety conditions on construction jobsites. It was apparent that lean design practices can be effectively employed in the design process to enhance construction site safety by facilitating design decisions and helping project teams to effectively incorporate prevention strategies into the physical design of a facility. The bottom-line is that lean design is an integral aspect of lean thinking, aiming at delivering waste reduction and value generation, and therefore should be broadly expanded within the AEC industry to improve safety management.
1. U.S. BLS (U.S. Bureau of Labor Statistics), 2015. National census of fatal occupational injuries in 2014: Preliminary results. U.S. Department of Labor.
2. Rajendran, S., Gambatese, J.A. and Behm, M. G., 2009. Impact of green building design and construction on worker safety and health. Journal of construction engineering and management, 135(10), pp.1058-1066.
3. Behm, M., 2005. Linking construction fatalities to the design for construction safety concept. Safety science, 43 (8), pp.589-611.
4. CDC (Centers for Disease Control and Prevention). 2016. The national institute for occupational safety and health (NIOSH): Hierarchy of controls, https://www.cdc.gov/niosh/topics/hierarchy/ (retrieved on August 1st, 2016).
5. Karakhan, A.A., 2016. Designer's liability: Why applying PTD principles is necessary. Professional safety, 61(4), pp.53.
6. Gambatese, J.A., Pestana, C.,. and Woo Lee, H. 2016. Alignment between lean principles and practices and worker safety behavior. Journal of construction engineering and management.
7. Karakhan, A.A., Gambatese, J.A., and Rajendran, S. 2016. Application of choosing by advantages decision-making system to select fall-protection measures. 24th annual conference of the international group for lean construction. Boston, USA.