This paper has attempted to reduce the uncertainty among design and construction professionals about site safety roles by theoretically analyzing their respective abilities to influence the root causes of accidents. The analysis (summarized in Table 4) indicates that under the traditional design-bid-construct project arrangement, subcontractors have a high ability to influence root causes, general contractors have a moderate ability to influence root causes, A/Es have a mixed ability to influence root causes, and owners have a low ability to influence root causes.