Road vehicles are characterized by increasing levels of automation and it is vital to understand the future impact on transport efficiency. Adaptive Cruise Control (ACC) is one of the first and most common automated functionalities available in privately owned vehicles. The effect of ACC on traffic flow has been widely studied by making assumptions on its operating strategy and on some of its important parameters such as the response time and the desired time headway. In the literature, these parameters are usually set to low values, based on the vehicle controller’s theoretical ability to respond within a very short time frame. Response time is known to be an important parameter in defining the capacity of the road and therefore, assuming a very short response time, studies usually conclude that systems like the ACC will contribute increasing the road capacity significantly. The present study aims at measuring the actual response time of an ACC-enabled vehicle in car-following conditions. A new methodology for the estimation of the controller’s response time and the desired time-gap was developed to this objective. Results show that the response time of the particular ACC controller was in the range 0.8s-1.2s, which is similar to what is commonly assumed for human drivers. In this light, the results of the present study question the common assumption that ACC or other automation technologies necessarily improve traffic flow and increase road capacity.

中文翻译：

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自适应巡航控制的响应时间和时距。对道路通行能力的实证特征和潜在影响

道路车辆的特点是自动化水平不断提高，了解未来对运输效率的影响至关重要。自适应巡航控制 (ACC) 是私人车辆中最早和最常见的自动化功能之一。通过对其运行策略及其一些重要参数（例如响应时间和所需的时距）进行假设，已经对 ACC 对交通流量的影响进行了广泛的研究。在文献中，根据车辆控制器在极短时间范围内响应的理论能力，这些参数通常设置为较低的值。众所周知，响应时间是定义道路通行能力的一个重要参数，因此，假设响应时间非常短，研究通常得出结论，像 ACC 这样的系统将有助于显着提高道路通行能力。本研究旨在测量启用 ACC 的车辆在跟车条件下的实际响应时间。为此开发了一种用于估计控制器响应时间和所需时间间隔的新方法。结果表明，特定 ACC 控制器的响应时间在 0.8s-1.2s 范围内，这与人类驾驶员通常假设的相似。有鉴于此，本研究的结果质疑 ACC 或其他自动化技术必然会改善交通流量和增加道路通行能力的普遍假设。为此开发了一种用于估计控制器响应时间和所需时间间隔的新方法。结果表明，特定 ACC 控制器的响应时间在 0.8s-1.2s 范围内，这与人类驾驶员通常假设的相似。有鉴于此，本研究的结果质疑 ACC 或其他自动化技术必然会改善交通流量和增加道路通行能力的普遍假设。为此开发了一种用于估计控制器响应时间和所需时间间隔的新方法。结果表明，特定 ACC 控制器的响应时间在 0.8s-1.2s 范围内，这与人类驾驶员通常假设的相似。有鉴于此，本研究的结果质疑 ACC 或其他自动化技术必然会改善交通流量和增加道路通行能力的普遍假设。