Effects of physical fatigue superimposed on high temperatures on construction workers’ cognitive performance

•Physical fatigue significantly impaired cognitive performances.•Fatigue level impacts the degree of negative effects on cognitive performances.•High temperatures significantly increased mental workload and mental fatigue.•Negative effects of physical fatigue increased when combined with heat exposure. Effects of physical fatigue on construction safety have been widely investigated, but it fails to examine the effects when physical fatigue is combined with adverse environmental conditions. This study investigated the combined effects of physical fatigue and high temperatures on workers’ safety-related cognitive performances, including mental workload, mental fatigue, and attention. A within-subject (n = 20) experiment was designed, where subjects suffered non-fatigued and three fatigued (low, medium, and high levels) conditions, both in normothermic and hyperthermic conditions. Their cognitions were recorded using an electroencephalogram (EEG) device while performing cognitive tasks. It indicates that physical fatigue significantly impaired cognitive performances; when the heat was superimposed on physical fatigue, the negative effects of physical fatigue on cognition were magnified; the cognitive impairments would further undermine task performance. The findings would help expand the understanding of the effects of physical fatigue on construction safety, and also provide a theoretical basis for implementing safety management measures in job sites with heat exposure.