Traffic congestion and crash rates can be reduced by introducing variable speed limits (VSLs) and automatic incident detection (AID) systems. Previous findings based on loop detector measurements have revealed that drivers reduce their speeds while approaching traffic congestion when the AID system is active. Notwithstanding these behavioural effects, most microscopic traffic flow models assessing the impact of VSLs do not describe driver response accurately.

This study analyses the main factors that influence driver deceleration behaviour while approaching traffic congestion with and without VSLs. The Dutch VSL database was linked to the driver behaviour data collected in the UDRIVE naturalistic driving study. Driver engagement in secondary tasks and glance behaviour were extracted from the video data. Linear mixed-effects models predicting the characteristics of deceleration events were estimated.

The results show that the maximum deceleration is high when approaching a slower leader, when driving at high speeds and short distance headways, and close to the beginning of traffic congestion. The minimum time headway is short when driving at high speeds and changing lanes. Certain drivers showed higher decelerations and shorter time headways than others. Controlled for these main factors, smaller maximum decelerations were found when the VSLs were present and visible, and when the gantries were within close proximity. These factors could be incorporated into microscopic traffic simulations to evaluate the impact of AID systems on traffic congestion more realistically. Further research is needed to clarify the link between engagement in secondary tasks, glance behaviour and deceleration behaviour.

通过引入可变速度限制（VSL）和自动事件检测（AID）系统，可以减少交通拥堵和崩溃率。先前基于环路检测器测量的发现表明，当AID系统处于活动状态时，驾驶员在降低交通拥堵的同时降低了速度。尽管有这些行为影响，但大多数评估VSL影响的微观交通流模型仍无法准确描述驾驶员的反应。

这项研究分析了在有和没有VSL的情况下，在接近交通拥堵时影响驾驶员减速行为的主要因素。荷兰VSL数据库已链接到UDRIVE自然驾驶研究中收集的驾驶员行为数据。从视频数据中提取驾驶员从事次要任务和扫视行为。估计了预测减速事件特征的线性混合效应模型。

结果表明，在靠近较慢的前导杆时，在高速行驶和短距离行驶以及接近交通拥堵开始时，最大减速度较高。高速行驶和改变车道时，最短时间间隔很短。某些驾驶员比其他驾驶员表现出更高的减速度和更短的行驶时间。在这些主要因素的控制下，当存在且可见的VSL以及门架非常接近时，可以发现较小的最大减速度。这些因素可以纳入微观交通模拟中，以更实际地评估AID系统对交通拥堵的影响。需要进一步的研究来阐明从事次要任务，扫视行为和减速行为之间的联系。