Informing drivers about the predicted state of upcoming traffic lights is considered a key solution to reduce unneeded energy expenditure and dilemma zones at intersections. However, newer traffic lights can react to traffic demand, resulting in spontaneous switching behavior and poor predictability. To assess whether future traffic light assistance services are viable, it is crucial to understand how strongly predictability is affected by such spontaneous switching behavior. Previous studies have so far only reported percentages of adaptivity-capable traffic lights, but the actual switching behavior has not been measured. Addressing this research gap, we conduct a large-scale predictability evaluation based on 424 million recorded switching cycles over four weeks for 18,009 individual traffic lights in Hamburg. Two characteristics of predictability are studied: cycle discrepancy and wait time diversity. Results indicate that fewer traffic lights exhibit hard-to-predict switching behavior than suggested by previous work, considering a reported number of 90.7% adaptive traffic lights in Hamburg. Contrasting previous work, we find that not all traffic lights capable of adaptiveness may necessarily exhibit low predictability. We critically review these results and derive avenues for future research.

翻译：通过向驾驶员预告前方交通灯状态，被视为减少交叉口不必要能耗与困境区域的关键解决方案。然而，新型交通灯可根据交通需求动态响应，导致切换行为具有自发性及低可预测性。为评估未来交通灯辅助服务的可行性，亟需理解这种自发性切换行为对可预测性的影响程度。既有研究仅报告了具备自适应能力的交通灯占比，但未实际测量其切换行为特征。为填补这一研究空白，我们基于汉堡市18,009个交通灯四周内记录的4.24亿次切换周期，开展了大规模可预测性评估。研究聚焦两个可预测性特征：周期差异度与等待时间多样性。结果表明，尽管汉堡自适应交通灯报告占比达90.7%，但相较于既有研究，实际呈现难以预测切换行为的交通灯数量更少。与既往结论相悖，我们发现并非所有具备自适应能力的交通灯必然表现出低可预测性。本文对此进行批判性审视，并提出了未来研究方向。