Air quality is a widespread problem with the presence of pollutants in indoor and outdoor environments that generate significant consequences for the population, ecosystems and exposed materials. Vehicular traffic is one of the main sources of air pollutants and, therefore, needs to be studied and analysed in detail.

This review reported the results of studies conducted on tunnels, in particular for the measurement of concentrations and the definition of emission factors. The characteristics of the tunnels, available ventilation systems, type of vehicular traffic, and geographical distribution, in addition to concentrations and emission factors, are discussed. Light-duty vehicles are the most frequent category in the case studies. Between the fuels used, gasoline is by far the most widespread.

Pollutant concentrations concentrations can reach very high levels. For example, atmospheric particulates (with an aerodynamic diameter of 10 µm) and nitrogen dioxide have also reached levels of 1490 µg/m³ and 4982 µg/m³, respectively.

空气质量是一个普遍存在的问题，室内和室外环境中都存在污染物，这些污染物会对人口，生态系统和暴露的物质产生重大影响。车辆交通是空气污染物的主要来源之一，因此需要详细研究和分析。

这篇评论报告了在隧道上进行的研究结果，特别是浓度测量和排放因子的定义。除了浓度和排放因子外，还讨论了隧道的特征，可用的通风系统，车辆交通的类型和地理分布。轻型车辆是案例研究中最常见的类别。在所使用的燃料之间，汽油是目前使用最广泛的燃料。

污染物浓度可以达到很高的水平。例如，大气微粒（空气动力学直径为10 µm）和二氧化氮也分别达到了1490 µg / m ³和4982 µg / m ^3的水平。