Study on the Relations between Drivers' Behavior and Road Alignments and Visual Environment at Sag Sections on Expressways.

在本研究中，我们关注高速公路凹陷路段驾驶员行为与道路线形和视觉环境的关系。本研究的主要观点如下：(1)第二章的重要结论如下。(1)定量地阐明了影响信号交叉口起动与稳定跟车之间加速度特性的三个因素。本文分析的因素包括驾驶员属性、车辆启动时信号交叉口车头时距、前车稳定车速等。同时也澄清了司机年龄的影响是显著的。②驾驶员属性对不同路段的影响具有共性。结果表明，在平坦或倾斜路段，老年驾驶员的加速度比其他驾驶员小，而在下降路段，老年驾驶员的加速度比其他驾驶员大。这些观测结果在简单的倾斜和下降剖面以及凹陷剖面上都得到了证实。(3)在下沉段，由于下降段车头时距变小，在下沉段底部和升级段产生较大减速的行驶模式。这种减速模式与平坦面积加速度之间的关系没有观察到。这意味着即使是在平地上缓慢加速的老年司机也可能有突然减速的风险。(2)利用驾驶模拟器采集驾驶员在凹陷路段的行为数据。为了明确驾驶员行为的决策过程，本研究采用了“协议分析法”。方案分析的主要结果是获得了排除数据的依据，并发现激发驾驶员识别倾斜度变化的重要性。驾驶员行为数据的分析结果表明，所提出的提高垂直弯道半径和正面能见度的方案是有效的。(3)一个被试使用模拟器进行重复实验，产生仅由一个特定驾驶行为参数构成的队列交通流。这些流对10个科目产生，发现这种均匀的流仍然形成一种激波现象。另一方面，进行了另一种类型的实验，即在7种道路垂直线形上产生由几个主体组成的排交通流。垂向排列的条件在凹陷段上下游坡度的代数差（“代数坡度差”）和垂向曲线长度上是不同的。试验结果表明，凹陷段坡度变化不大的地方产生减速激波，坡度变化不大的地方也产生减速激波。交通流主体的某些特殊特性可能引起减速激波。少

In this study, we concern the relations between drivers' behavior and road alignments and visual environment at sag sections on expressways. The major point of this study are as following :(1) Important results of chapter-2 are as follows. 1) It was quantitatively clarified that three factors influenced characteristics of the acceleration between the starting at signalized intersection and the stable following driving. Factors analyzed here, are the attributes of drivers, time headway at the signalized intersection the vehicle started, and the stable speed of leading vehicle. It was also clarified that the effect of drivers' age is significant. 2) The effect of the drivers' attributes had common effects to different road sections. It was confirmed that acceleration of aged drivers is lower than the others at flat or incline section, and is more than the others at decline section. These observations were confirmed at simple incline and decline section as well as sag section. 3) At sag s … More ection, driving pattern that relatively big deceleration was generated in sag bottom and upgrade interval because the headway became small at decline section. The relationship between such deceleration pattern and acceleration of flat area was not observed. This means that even aged drivers with gentle accelerating at flat area may have risk of such sudden decelerating.(2) The data of drivers' behavior at sag section were collected with driving simulator. And in order to make clear the decision-making process of drivers' behavior, the present study used "protocol analysis". The main result of protocol analysis is that the grounds to exclude the data were obtained and it was found out that rousing drivers to recognize the change of inclination is important. Analysis results of the data of drivers' behavior revealed the effectiveness of the alternative proposed for improvement of radius of vertical curves and frontal visibility(3) The repetition experiment by one subject using the Simulator produces platoon traffic stream made of only one particular driving behavior parameter. Those streams are produced for ten subjects, and it is found that such uniform stream still form a kind of shock wave phenomena. On the other hand, another type of experiment, which produces platoon traffic streams made by several subject on seven types of road vertical alignment, is carried out. The condition of vertical alignments is different in algebraic difference of upstream and down stream grade at a sag section ('algebraic grade difference') and in 'vertical curve length'. The experiment shows that not most steep grade change of sag sections produces deceleration shock wave and also most gentle grade change does it. Some particular characteristics of a subject of traffic stream might cause deceleration shock wave. Less