Variable speed limit control for severe non-recurrent freeway bottlenecks

Variable speed limit (VSL) schemes are developed based on the Kinematic Wave theory to increase discharge rates at severe freeway bottlenecks induced by non-recurrent road events such as incidents or work zones while smoothing speed transition. The main control principle is to restrict upstream demand (in free-flow) progressively to achieve three important objectives: (i) to provide gradual speed transition at the tail of an event-induced queue, (ii) to clear the queue around the bottleneck, and (iii) to discharge traffic at the stable maximum flow that can be sustained at the bottleneck without breakdown. These control objectives are accomplished without imposing overly restrictive speed limits. We further provide remedies for (a) underutilized bottleneck capacity due to underestimated stable maximum flow and (b) a re-emergent queue at the bottleneck due to an overestimated stable maximum flow. We analytically formulate the reductions in total delay in terms of control parameters to provide an insight into the system performance and sensitivity. The results from the parameter analysis suggest that significant delay savings can be realized with the proposed VSL control strategies.     

Rail vehicles,environment, safety and security

This paper starts with a discussion on typical vehicles. The concepts and the usual practice for rail wagon design, both freight and passengers are presented. A discussion on rail and the environment comes next followed by Truck-Trains. Accident theories, metaphors and investigation methods are widely discussed; Hazard – Barrier – Target Model, Swiss Cheese Model, Bow-Tie Model, Fault Tree Analysis and Event Tree Analysis are explained. This paper concludes with a technical discussion on safety and security of rail vehicles, standards for safety and measures against terrorist attacks.     

ITS中突发事件的智能对策

当今社会,科学技术在不断发展,但社会中各种危机、事故的发生概率不但没有降低反而在不断升高,这成为制约社会发展和进步的重要因素。特别是"9.11"的发生,对于全世界人民是一次强烈的冲击。ITS作为一种新型的交通管理手段,在交通系统这个复杂大系统中具有相当的复杂性和不确定性,一个小小的突发事件就会引起发严重的交通灾难,因此对突发事件的研究就显得尤为重要。本文在总结众多国内外资料后,提出了"突发事件就是使物元产生重大改变的事件"这一全新概念。以这个概念为基础,以ITS为技术支持,结合模糊数学、可拓学、界壳论等方法,探索如何利用模糊控制,可拓力与潜可拓力建造防御界壳,有效控制交通系统中突发事件发生的方法。     

基于V-支持向量分类机的交通事件检测方法研究

基于支持向量机在解决分类问题的优势，本文提出基于V-支持向量分类机的交通事件检测方法。首先把交通事件是否发生看成是一个特殊的分类问题，选取V-支持向量分类机和核函数，根据以往的交通事件是否发生的检测数据，即分别在发生交通事件和不发生交通事件两种情况下的上下游车道占有率，计算出其当前时段的上下游车道占有率的绝对差、相对差，以及下游前两时段与当前时段车道占有率的相对差，以此作为V-支持向量分类机的输入，对其进行训练，然后输入现阶段检测到的相应车道占有率统计结果，利用训练完成的V-支持向量分类机来判别是否发生交通事件。最后，本文以微观交通模拟的数据验证模型的效果。