An important task in the collaborative human-robot work-space development is ensuring operator safety. Setting up global restriction for the overall robot movement based on worst-case scenario leads to a decrease in efficiency and increase of working time. Considering safety precautions in the motion planning phase may help to satisfy the safety of the operator while keeping the production time effective. In this study, several methods of including safety into motion planning are proposed and evaluated. Safety of the operator is defined based on technical specification ISO/TS 15066  and the principle of energy absorption by the operator body. Simulations of regulated robot movement are based on model scenario captured in an experimental workplace with assistant co-working manipulator PaDY. Velocity limits for the robot are drafted according to predicted operator trajectory. By using the proposed method, we have been able to reduce the relative velocity during operation of the robot and reduce the risk of harming workers. We propose a method of relative velocity measurement and limiting. Finally, we compare the benefits and robustness of different methods.