肖琳

       如今，恶劣天气的发生和交通事故的频发已对社会、经济造成了严重的负面影响，占道施工以及大型活动的频繁出现也对公共资源的合理配置提出了更高的要求。交通系统面临以上异于常规的事件和活动时将打破自身的自组织平衡，使得运行车流发生紊乱并产生大规模的交通拥挤。由此，交通系统不得不应对特殊事件和活动对系统提出的多样化需求，这使得特殊需求本身成为了近年来公众和学者关注的热点问题。

       然而，当前与特殊需求相关的研究多停留在交通流参数的影响层面，未深入分析特殊需求与交通拥挤形成、传播之间的作用机制，也缺乏必要的理论推导和数据验证。这使得特殊需求影响下交通拥挤的形成、发展和空间演变规律仍未被了解和掌握，交通管理者也无法依据特殊拥挤的演变特征进行合理地策略决策。因此，本文的研究目的在于提取特殊交通需求影响下的拥挤形成及传播规律，建立网络态势评估方法，为实施面向特殊需求的交通管理提供坚实的理论基础和实践方法。

       首先，研究结合特殊需求特征和拥挤影响因素的分析，界定了基于路网车速下降、局部通行能力受损和需求集中分布三个不同拥挤主导因素的特殊交通场景，并分别采用路网容量理论、瓶颈点车辆排队累计图和交通资源竞争分析来阐述交通拥挤的形成机理。然后，基于交通波理论在连续流和间断流的应用，研究刻画了特殊交通场景中拥挤的传播过程，并对拥挤传播条件和传播速度进行了理论公式推导，发现特殊场景中拥挤传播的临界条件更易得到满足，且传播速度均大于一般情况。接着，研究分析了交通状态评价指标在特殊场景中的有效性和适应性，并结合特殊需求的运行特征建立了用于多场景的网络交通态势评估流程和算法，能提高交通状态估计的准确性并扩大其使用范围。最后，研究通过北京、上海的快速路数据分析，分别得到暴雨条件和事故条件下交通流参数、拥挤特征和传播模式等的变化，并与理论研究成果进行对照和验证，发现结论基本一致。理论分析和实例验证相结合的方法将分别从定性和定量的角度研究特殊需求对交通拥挤的影响，既避免了特殊数据不足和假设条件影响的研究境况，也获得了可靠的参数变化趋势和定量化影响程度。

       本文综合、系统地研究了特殊需求对交通系统产生的影响，揭示了交通拥挤形成及传播的发展规律，对交通流理论进行了补充，完善了交通态势估计的理论方法，对未来实施特殊需求的交通管理具有十分重要的理论意义。

关键词：特殊交通需求，交通拥挤传播机理，交通波理论，交通拥挤态势估计

     Nowadays, the frequent occurrences of severe weather and traffic accident have caused serious negative impacts on society and economy and the numerous appearances of road maintaince and large-scale activity have also required more reasonable allocation of public resources. Facing these unconventional condtions, the balance of self-organization of traffic system will be broken and lead to disorderd traffic steam and massive congestion. Therefore, traffic system has to deal with the diverse requirements of special conditions, which makes the spcial conditions become an attracting issue for public and researchers in recent years.

     However, the existing study related to special condtions simply focused on the traffic parameter influences instead of analyzing the interactions between special condtions and formation and propagation mechanism of traffic congestion, lacking necessary theory deduction and data verification. Thus, the law of development and spatial evolution of traffic congestion has not yet been understood and mastered, which cannot provide sufficient information to the traffic manager for making reasonab strategy decisions. The purpose of this research is to extract the law of formation and propagation of traffic congestion under special conditons, establish a network trend assessment method for traffic congestion and provide a solid theory foundation and a pratical method for traffic incident management.

     This research begins with characterists analysis of special conditions combined with congestion influence elements. After defining three special scenarios based on different dominant congestion factors: network speed decreased, partial capacity reduction and demand concentrated distribution, this research interprets the formation of traffic congestion by using Network Capacity Theory, vehicles accumulation analysis in bottleneck and traffic resouces competention analysis in seperatively.

Secondly, based on the application of Wave Theory in continuous flow and interrupted flow, this research describes the propagation processes of traffic congestion and derives the formulas of critical requirements and velocities of propagation. The result indicates that the critical propagation requirements in special secenarios are more achievable and the velocities are greater than the normal situation.

     Thirdly, this research analyses the effectiveness and adaptability of traffic evaluation indexs in special scenarios and establishs network trend assessment processes for traffic congestion combining with operational characteristics of special scenarios, which will enhance the accurancy and applicability of traffic performance assessment.

Eventually, this research obtains the variation of traffic steam parameters, congestion characteristics and propagation modes under the condtions of storm weather and traffic accident seperatively, throught the detected traffic datas from urban fressways in Beijing and Shanghai. Then, by comparing the results from theoretical analysis, the data analysis verifies the validity of theoretical deduction. The methodology which combines theoretical analysis with data analysis will allow proceding the research both from qualitative and quantitative aspects, avoid the situation of insufficient datas and being influenced by preset condtions and acquire reliable variation trend and level of impact.

     In this research, the impacts of special conditions on traffic system have been studied in comprehensive and systematic way. This paper reveals the law of formation, development and propagation of traffic congestion, replenishs the basic traffic flow theory and improves the theoretical methods for congestion assessment, which playing a significant role in traffic incident management in the future.

Key Words: special traffic conditions, traffic congestion propagation, Wave Theory, Traffic congestion trend assessment