# Modelling Prefabricated Construction Safety
## 3 Results and Discussion
### Injuries in Prefabricated Construction Accidents
#### 3.6.4 Primary Injury Site  
Figure 17 shows the number of accidents under injury site (location on human body) for PCC. The X-axis represents the years, and the y-axis represents the percentages of occurrence. There are around 41% unknown injury sites reported in the last five years. Otherwise, top injury sites, in ascending order, are 'lower back/spine' (19%), 'finger/thumb' (17%), 'hand/wrist' (10%),'shoulder' (6%), 'upper and lower arm' (4%), 'eye' (2%) and 'knee' (1%). 'Shoulder' injury is only associated with Alum, Wood_S, Metal_S, and Metal_P in ascending order. 'Eye' injury is associated with Metal_S, Metal_P, Wood_P, and Conc in ascending order. 'Knee' injury is only associated with Conc and Wood_P. 'Upper and lower arm' injury is only associated with Wood_S and Alum in ascending order. Overall, in last five years, there is decline in 'finger/thumb', 'eye', 'upper and lower arm', and 'knee'; 'hand/wrist' and'shoulder' injuries slightly increased over this period. 'Lower back/spine' is relatively less fluctuating than the 'unknown' category. Figure 18 shows a comparison between offsite and onsite. The top two injury sites are similar, but the rest vary, such as 'lower back/spine' (16%), 'finger/thumb' (16%), 'eye' (10%), 'hand/wrist' (8%), 'knee' (6%), and 'unknown' (45%). Lower back/spine is three times, finger/thumb is five times, hand/wrist is three times, eye is eighteen times, and knee is seventeen times higher compared to onsite. It seems offsite workers are more prone to obtain injuries on'shoulder' and 'upper and lower arm', but are less likely to obtain an 'eye' injury. However, they are more likely to obtain 'lower back/spine' injuries, which indicates poor ergonomics in an offsite working environment. Interestingly, ear location is more vulnerable offsite. Figure 16: ARIMA models for accident forecasting by prior activities to critical injuries (2017–2027). Figure 17: Number of accidents by injury site in prefabricated construction (2017–2022). Figure 18: Comparison of number of accidents by most common injury location (2017–2022). Injury sites were modelled with simplistic equations to determine the weightage of each site under each classification. This helps to determine the critical sites of accidents and is useful for ergonomics. \[\text{Injury site (Wood\_S) = 20 \times Lower back/spine + 19 \times Finger/thumb + 10 \times Hand/wrist + 7 \times Shoulder} \tag{34}\] \[\text{+ 6 \times Upper and lower arm + 39 \times Other}\] \[\text{Injury site (Conc) = 17 \times Lower back/spine + 14 \times Finger/thumb + 9 \times Hand/wrist + 7 \times Eye}\] (35) \[\text{+ 6 \times Knee + 47 \times Other}\] \[\text{Injury site (Alum) = 20 \times Lower back/spine + 15 \times Finger/thumb + 10 \times Hand/wrist + 10 \times Shoulder}\] (36) \[\text{+ 6 \times Upper and lower arms + 40 \times Other}\] \[\text{Injury site (Metal\_S) = 18 \times Lower back/spine + 14 \times Finger/thumb + 10 \times Eye + 9 \times Hand/wrist}\] (37) Figure 17:0 Figure 17:1 (38) Figure 17:2 Figure 17:3 Figure 17:4  
In this section, accident frequency is forecast for the injury sites. Table 7 and Figure 19 show the optimized ARIMA models for each injury site. The main trend is that 'finger/thumb', 'upper and lower arm', and 'knee' are declining, but 'lower back/spine' and 'hand/wrist' are somehow steady. However,'shoulder' and 'eye' have an increasing trend. The Workforce in offsite construction needs to use proper personal protective equipment such as a body harness and eye protection to avoid injuries.