Prior safety evaluations of interchange merging areas have mostly focused on traffic conflicts and operating speeds, without considering how these factors can influence the driver workload. Researches regarding the level of driver workload have largely concentrated on urban roads, tunnel sections, and basic freeway segments, without considering the impact of merging traffic flows on safety. Therefore, this study has investigated how merging vehicles can impact through-driver workload and safety. Three independent field experiments were conducted on freeways, involving 18 drivers and 17 interchanges. The results showed that the vehicles merging onto freeway impact driver workload and driving performance, generating potential risk that cannot be ignored. Merging into the mainline traffic flow increases the through-driver workload to a higher level or even exceeds the safety threshold, despite there being better geometrical conditions of interchanges than those of basic freeway segments. When the volume of merging vehicles exceeds 564 pcu/h or the traffic saturation is above 0.485, driver workload rises above the safety thresholds and the driving risk is elevated, which potentially would lead to crashes. This study offers insights for more effective segment division of operating speed prediction, and dynamic risk management with regard to interchange safety.

以往对互通立交汇流区的安全评估主要关注交通冲突和运行速度，而没有考虑这些因素如何影响驾驶员的工作量。关于驾驶员工作负荷水平的研究主要集中在城市道路、隧道路段和高速公路基础路段，没有考虑合流交通流对安全的影响。因此，本研究调查了并道车辆如何影响驾驶员的工作量和安全性。在高速公路上进行了 3 次独立的现场实验，涉及 18 名驾驶员和 17 个立交桥。结果表明，车辆并入高速公路会影响驾驶员的工作量和驾驶表现，产生不可忽视的潜在风险。尽管立交桥的几何条件比基本高速公路路段更好，但并入主线交通流会使直通驾驶员的工作量增加到更高水平，甚至超过安全阈值。当合流车辆量超过564 pcu/h或交通饱和度超过0.485时，驾驶员工作负荷超过安全阈值，驾驶风险升高，可能导致撞车事故。这项研究为更有效地划分运行速度预测以及立交安全方面的动态风险管理提供了见解。