Truck platooning is a promising solution for enhancing efficiency and reducing fuel consumption in freight transportation. However, overtaking truck platoons poses safety challenges that need to be addressed. This paper employs an overtaking model incorporating lane change dynamics, and a collision risk assessment to evaluate the safety risks involved in overtaking truck platoons. The safety assessment is presented through a numerical analysis that considers three aspects: roadway geometry, traffic conditions, and driver behavior. Scenarios representing different truck platoon lengths, driver behavior, and opposing traffic conditions are evaluated, highlighting their impact on safety. Two major findings from the assessment are that the overtaking distance and time increase linearly as the truck platoon length increases, and potential driver hesitation and the presence of opposing vehicles are shown to increase collision risks. Safety implications are that the length of truck platoons needs to be regulated on two-lane undivided highways; and driver behavior should be considered in the safety assessment and regulation of truck platooning, but further investigations are needed. From the perspective of overtaking, this paper emphasizes the need for safety guidelines and regulations for truck platooning. Policymakers, transportation agencies, and industry stakeholders may utilize the findings to establish standardized safety measures and protocols.