Conditionally automated driving requires drivers to resume vehicle control promptly when automation reaches its operational limits. Ensuring smooth vehicle control transitions is critical for the safety and efficiency of mixed-traffic transportation systems, where complex interactions and variable traffic behaviors pose additional challenges. This study addresses this challenge by introducing an adaptive time budget framework that provides drivers with sufficient time to complete takeovers both safely and comfortably across diverse scenarios. We focus in particular on the takeover buffer, that is, the extra time available after drivers consciously resume control to complete evasive maneuvers. A driving simulator experiment is conducted to evaluate the influence of different takeover buffer lengths on safety-related indicators (minimum time-to-collision, maximum deceleration, and steering wheel angle) and subjective assessments (perceived time sufficiency, perceived risk, and performance satisfaction). Results show that (i) takeover buffers of about 5-6 seconds consistently lead to optimal safety and comfort; and (ii) drivers prefer relatively stable takeover buffers across varying traffic densities and n-back tasks. This study introduces an adaptive time budget framework that dynamically allocates transition time by incorporating a predicted takeover time and a preferred takeover buffer (piecewise function). This can serve as an important first step toward providing drivers with sufficient time to resume vehicle control across diverse scenarios, which needs to be validated in more diverse and real-world driving contexts. By aligning the provided time budget with driver needs under specific circumstances, the adaptive framework can improve reliability of control transitions, facilitate human-centered automated driving, reduce crash risk, and maintain overall traffic efficiency.

翻译：条件自动驾驶要求驾驶员在自动化系统达到其运行极限时迅速接管车辆控制。确保车辆控制平稳转换对于混合交通系统的安全与效率至关重要，其中复杂的交互与多变的交通行为带来了额外挑战。本研究通过引入自适应时间预算框架应对这一挑战，该框架为驾驶员提供充足时间，使其能在多种场景下安全且舒适地完成接管操作。我们特别关注接管缓冲期，即驾驶员有意识地恢复控制后可用于完成规避操作的额外时间。通过驾驶模拟器实验，评估不同接管缓冲时长对安全相关指标（最小碰撞时间、最大减速度、方向盘转角）和主观评价（感知时间充足性、感知风险、表现满意度）的影响。结果表明：（i）约5-6秒的接管缓冲期能持续带来最优的安全性与舒适性；（ii）驾驶员在不同交通密度与n-back任务中偏好相对稳定的接管缓冲时长。本研究提出的自适应时间预算框架通过整合预测接管时间与偏好接管缓冲（分段函数）动态分配转换时间，可作为确保驾驶员在多样化场景中获得充足接管时间的重要初步探索，未来需在更广泛的实际驾驶环境中验证。通过使提供的时间预算与特定情境下的驾驶员需求相匹配，该自适应框架可提升控制转换的可靠性，促进以人为本的自动驾驶发展，降低碰撞风险，并维持整体交通效率。