Data from: Nature, extent and ecological implications of night-time light from road vehicles

1.The erosion of night‐time by the introduction of artificial lighting constitutes a profound pressure on the natural environment. It has altered what had for millennia been reliable signals from natural light cycles used for regulating a host of biological processes, with impacts ranging from changes in gene expression to ecosystem processes. 2.Studies of these impacts have focused almost exclusively on those resulting from stationary sources of light emissions, and particularly streetlights. However, mobile sources, especially road vehicle headlights, contribute substantial additional emissions. 3.The ecological impacts of light emissions from vehicle headlights are likely to be especially high because these are (i) focused so as to light roadsides at higher intensities than commonly experienced from other sources, and well above activation thresholds for many biological processes; (ii) projected largely in a horizontal plane and thus can carry over long distances; (iii) introduced into much larger areas of the landscape than experience street lighting; (iv) typically broad ‘white’ spectrum, which substantially overlaps the action spectra of many biological processes; and (v) often experienced at roadsides as series of pulses of light (produced by passage of vehicles), a dynamic known to have major biological impacts. 4.The ecological impacts of road vehicle headlights will markedly increase with projected global growth in numbers of vehicles and the road network, increasing the local severity of emissions (because vehicle numbers are increasing faster than growth in the road network) and introducing emissions into areas from which they were previously absent. The effects will be further exacerbated by technological developments that are increasing the intensity of headlight emissions and the amounts of blue light in emission spectra. 5.Synthesis and applications. Emissions from vehicle headlights need to be considered as a major, and growing, source of ecological impacts of artificial night‐time lighting. It will be a significant challenge to minimize these impacts whilst balancing drivers’ needs at night and avoiding risk and discomfort for other road users. Nonetheless, there is potential to identify solutions to these conflicts, both through the design of headlights and that of roads.1. 人工照明的普及侵蚀了夜间环境，对自然生态系统构成了严峻压力。数千年来，生物依托自然光周期(natural light cycles)作为调控众多生物过程(biological processes)的可靠信号，而人工照明已改变了这一信号系统，其影响涵盖从基因表达(gene expression)改变到生态系统进程(ecosystem processes)变化的诸多层面。 2. 现有针对此类生态影响的研究几乎仅聚焦于固定光源(stationary sources)产生的光辐射，尤以街道路灯为核心。然而，移动光源(mobile sources)——尤其是道路车辆前照灯(headlight)——亦贡献了可观的额外光辐射。 3. 车辆前照灯辐射光所带来的生态影响或尤为显著，原因如下：其一，其光束聚焦，照射路侧的光强高于其他常见光源，且远超众多生物过程的激活阈值(activation thresholds)；其二，光束多沿水平面(horizontal plane)投射，因此可传播至较远距离；其三，其覆盖的景观范围远大于街灯照明区域；其四，通常为宽谱“白光”，与众多生物过程的作用光谱(action spectra)高度重合；其五，路侧区域常因车辆通行而遭遇间歇性光脉冲(light pulses)，这种动态光辐射已被证实会产生重大生物学影响。 4. 随着全球车辆保有量与道路网络(road network)的规划增长，车辆前照灯带来的生态影响将显著加剧：一方面，车辆增速快于道路网络扩张，会提升局部光辐射的严重程度；另一方面，光辐射会侵入此前未受照明影响的区域。而当前技术发展正持续提升前照灯光辐射强度与光谱(spectrum)中的蓝光(blue light)占比，将进一步恶化此类影响。 5. 总结与应用。车辆前照灯的光辐射应被视为人工夜间照明生态影响的一项重要且日益严峻的来源。在兼顾夜间驾驶需求、避免对其他道路使用者造成风险与不适的前提下，最大限度降低此类影响，是一项极具挑战性的任务。尽管如此，通过优化前照灯设计与道路规划，仍有潜力找到化解此类冲突的解决方案。