通过可调参数实时优化公交优先与交通延误的平衡
Preference-Conditioned Multi-Objective Reinforcement Learning for Runtime-Tunable Transit Signal Priority
- 用偏好参数动态调节信号灯,无需重训即可切换公交优先等级
- 单个模型在不同偏好下实现平滑性能权衡,优于固定规则和基线方法
- 适合城市交通管理机构在不同时段灵活调整公交优先策略
公交信号优先(TSP)需在降低公交延误、限制非公交车辆影响及避免部分车辆极端等待之间取得平衡。现有强化学习方法通常编码公交特征但优化固定奖励或加权目标,导致当管理优先级随时段或突发情况变化时灵活性不足。本文提出一种偏好条件化的TSP控制器π(a∣s,w),在最小/最大绿灯时长与换相可行性约束下选择下一信号相位,可通过运行时偏好参数w调节公交优先与整体交通延误的权衡,无需重新训练。我们在IntersectionZoo基础上引入约束信号控制/TSP包装器,并通过公交密集度增强与基于时刻表的公交插入扩展场景生成,以应对训练中公交事件稀疏的问题。实验表明,单一学习到的条件化策略可在运行时偏好下覆盖平滑的性能权衡前沿,优于固定配时与规则基线,且保持约束可行性;尾部延迟诊断显示,在中等偏好设置下非公交外部性可控,但高公交优先权重下会显著增加。源代码见https://github.com/urbanAIthi/morl-tsp。
原文摘要 · Abstract (English)
Transit signal priority (TSP) requires balancing competing objectives: reducing bus delay while limiting adverse impacts on non-bus traffic and avoiding extreme waits for a subset of vehicles. Existing reinforcement-learning (RL) approaches to TSP typically encode transit-aware features (e.g., occupancy and schedule deviation) but optimize a fixed reward or fixed scalarization, which limits operational flexibility when agency priorities change across time-of-day or disruption conditions. We present a preference-conditioned TSP controller, $π(a \mid s,w)$, that selects the next signal phase under minimum/maximum green and transition-feasibility constraints and can be tuned at runtime via a preference parameter $w$ to trade off bus-priority emphasis against overall traffic delay without retraining. We implement this on top of IntersectionZoo by introducing a constrained signal-control/TSP wrapper, and we extend scenario generation with bus-prevalence augmentation and timetable-based bus insertion to address sparse transit-priority events during training. Experiments against fixed-time control, a rule-based TSP overlay, and fixed-weight PPO specialists show that a single learned conditioned policy spans a smooth empirical trade-off frontier across runtime preferences, outperforms fixed-time and rule-based baselines, and maintains constraint feasibility, while tail-delay diagnostics reveal that non-bus externalities remain limited for moderate preference settings but can increase substantially under high bus-priority weights. The source code of this work is available at https://github.com/urbanAIthi/morl-tsp.
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