# Improvements of Design for Safety in Construction through Multi-Participants Perception Analysis
## 3 Materials and Methods
### Definition of the DfS Improvement Alternatives  
As mentioned earlier, eight DfS improvement alternatives were deduced in this study, and the priority of such DfS alternatives for the improvement of DfS in South Korea as perceived by all respondents and the construction project participants, and by career level, are presented herein. [PERSON] and [PERSON] (2008) suggested four PtD alternatives through a literature review to improve PtD. Therefore, this study analysis previous studies, reports, and laws to deduce the DfS improvement alternatives, with eight found after this process [15]. As shown in Table 1, relevant studies, reports, and laws were considered before suggesting the following eight DfS improvement alternatives: (i) the application of extended coverage, (ii) adjustment of the application phase, (iii) application of the design alternatives, (iv) the development of a collaboration program, (v) the development of a training program for experts, (vi) involvement of  
Figure 1: Research process. the contractor in the pre-construction phase, (vii) the development of a decision support system, and (viii) the assignment of responsibility for DfS to the client. Explanations of the DfS Improvement Alternatives  
(i) Application of extended coverage: In South Korea, DfS is applied only to public construction projects that exceed a specific size (e.g., buildings with more than ten stories, buildings with excavations exceeding 10 m) [17]. In addition, in South Korea, the number of private construction projects is more than three times the number of public construction projects [19]. Thus, the number of DfS-eligible construction projects in South Korea is very small compared to the size of the overall construction industry in the country. On the other hand, CDM in the UK can be applied to construction projects with a construction period of 30 days or more or with more than 20 construction workers, as well as to those with more than 500 construction workers per day [11]. In addition, Safe Design in Australia is applied to all construction projects worth over AUD $250,000 [13], and DfS in Singapore is applied to all construction projects worth over SGD $100,000 [14]. As such, overseas DfS is applied to all construction projects regardless of whether they are public or private [30]. In addition, PtD in the U.S. is a national strategy that has not been legislated, unlike in other countries, and its application to construction projects is simply a recommendation and not a requirement. The U.S., however, is attempting to induce the application of PtD by providing extra points for LEED certification to those cases where PtD is implemented [12]. (ii) Adjustment of the application phase: DfS in South Korea is supposed to be implemented upon 80% completion of the construction document preparation phase [17], when most of the design outputs have been completed. In this case, however, even if a situation where a design change is required through the DfS process occurs, there is no institutional basis for additional costs and design period extensions. Therefore, it is not easy for construction project clients and designers proactively to suggest design alternatives and reflect these in the construction document. With the application of DfS, a design change requires more collaboration, additional processes, and incurs more costs as the construction life cycle progresses [28; 32]. According to the MacLeamy curve, the impact of a change in the construction project decreases gradually from the design phase to the construction and operating and maintenance phases. Conversely, the cost required for the implementation of a change in the construction project increases as the operating and maintenance phases approach [41]. Therefore, DfS is more effective when implemented in the conceptual phase, which is the initial design stage. In addition, it is advisable to implement DfS upon 10, 30, 60, and 90% completion of the design phase [27; 33].