Impact on energy and air quality of connected and autonomous vehicles in an urban context

Despite numerous studies related to autonomous vehicles and connected vehicles (CAVs) and their impact on the economy or on traffic performance (eg, flow management, accidents), there are not many studies that relate these benefits to the environmental component. In this context, the objective of this work consisted in the integrated assessment of the impacts of CAVs on traffic performance, atmospheric emissions CO₂ and NO_x,and air quality. To this end, a roundabout in the city of Aveiro was selected as a case study, and different scenarios were created: base scenario, considering the current typology of vehicles (conventional); scenario 2, considering defensive behavior CAVs; scenario 3, considering assertive behavior CAVs; and scenario 1, considering all types of vehicles mentioned above. To ensure a comprehensive analysis, all scenarios were evaluated for a period of 24 hours, corresponding to the period of the experimental campaign carried out, and a cascade of models was applied. First, the PTV VISSIM model was applied which allowed, configuring, calibrating and validating the network under study for an evaluation of the traffic performance. Second, the VSP model was applied to estimate atmospheric emissions, Finally, the CFD VADIS model was applied to air quality assessment. The results obtained allowed us to conclude that the introduction of CAVs, promotes longer travel times, especially during times of higher traffic, and an increase in emissions, mainly by the CAVs with defensive behavior. In terms of air quality, there were large differences in terms of NO₂ concentrations, with the CAVs promoting a degradation of air quality, especially during peak traffic hours.尽管现有诸多针对自动驾驶汽车与联网自动驾驶车辆（Connected and Automated Vehicles，CAVs）及其对经济或交通运行性能（如流量管控、事故防控）的相关研究，但鲜有将这类技术的效益与环境维度相结合的研究。在此背景下，本研究的目标是综合评估联网自动驾驶车辆（CAVs）对交通运行性能、大气二氧化碳（CO₂）与氮氧化物（NOₓ）排放以及空气质量的影响。为此，本研究选取阿威罗市的一处环岛作为案例研究对象，并设置了多组对比场景：基准场景，采用当前主流的传统燃油车辆类型；场景2，搭载防御型驾驶行为的联网自动驾驶车辆；场景3，搭载主动型驾驶行为的联网自动驾驶车辆；以及场景1，涵盖上述所有类型的车辆。为保障分析的全面性，所有场景均按照本次实验活动的时长，以24小时为周期进行评估，并采用了级联模型体系。首先，应用PTV VISSIM模型对研究路网进行配置、校准与验证，以此开展交通运行性能评估；其次，应用车辆比功率（Vehicle Specific Power，VSP）模型估算大气污染物排放量；最后，应用CFD VADIS模型开展空气质量评估。研究结果表明，联网自动驾驶车辆的引入会延长出行时长，尤其在交通高峰时段更为显著，同时会增加污染物排放量，其中搭载防御型驾驶行为的车辆排放量增幅尤为明显。在空气质量方面，二氧化氮（NO₂）浓度存在显著差异：联网自动驾驶车辆的应用会导致空气质量恶化，尤其在交通高峰时段这一现象更为突出。