Among all 33 TBL sustainability criteria, the social SPI “work- force health and safety” is the only criterion that was ranked first among both the overall TBL SPIs and the social category it belongs to. This SPI is a “very high” importance SPI with an impressive SI value of 91.25%, which is higher than the SI values of the economic and environmental top ranked SPIs. This indicates the significance of the health and safety of the workers to the overall sustainability of a building from the construction experts' perspectives, and points to their belief that the modular and conventional processes can provide extremely different degrees of labor health and safety in building projects. In fact, on-site reportable accidents can be decreased up to 80% using off-site construction processes (Lawson et al., 2012). By performing the main work in manufacturing cen- ters (rather than on the final project sites) working at height, dangerous activities, severe weather, congestion, workplace acci- dents, and neighboring construction operations can be decreased (McGraw-Hill Construction, 2011; Na, 2007; Li et al., 2013; Haas and Fagerlund, 2002).
- reduction in elevated work and dangerous activities
- reduction in on-site workforce congestion
- less workforce exposure to neighboring construction operations
- less workforce exposure to severe weather
- less working time on-site
- controlled manufacturing facilities