Integrated models of land use and transportation for the autonomous vehicle revolution

ABSTRACT

The advent of the autonomous vehicle (AV) will affect not only the transportation system, but also future patterns of land development. Integrated land use and transportation models will be critical tools in assessing the path forward with this technology. Key questions with respect to land use impacts of AVs arise from potential changes in sensitivity to travel and reduced demand for parking. It is an open question whether AVs will induce urban sprawl, or whether spatial economies of agglomeration will mitigate any reductions in travel time sensitivity. The deployment of shared fleets of AVs would likely reduce parking demand, producing yet to be explored impacts on property development within existing urban footprints. We perform a critical assessment of currently operational models and their ability to represent the adoption of AVs. We identify the representation of time in such models as a vital component requiring additional development to model this new technology. Existing model applications have focused on the discrete addition of new infrastructure or policy at a fixed point in time, whereas AV adoption will occur incrementally through time. Stated adaptation surveys are recommended as tools to quantify preferences and develop relevant model inputs. It is argued that existing models that assume comparatively static equilibrium have been convenient in the past, but are insufficient to model technology adoption. In contrast, dynamic model frameworks lack sufficient structure to maintain reasonability under large perturbations from base conditions. The ongoing advancement of computing has allowed models to move away from being mechanistic aggregate tools, towards behaviourally rich depictions of individual persons and firms. However, much work remains to move from projections of existing conditions into the future, to the evolution of the spatial economy as it evolves through time in response to new technologies and exogenous stresses. Principles from complex and evolutionary systems theory will be important in the development of models with the capacity to consider such dynamics.     

Development of Green-Naghdi models with a wave-absorbing beach for nonlinear, irregular wave propagation

Two-dimensional and three-dimensional Green-Naghdi (GN) models equipped with a numerical wave-absorbing beach have been developed to simulate nonlinear, regular, and irregular wave propagation. The numerical beach is introduced near the downstream boundary to absorb outgoing waves. An appropriate amount of numerical damping and an appropriate length of numerical beach are investigated using numerical experiments. The results show that the GN models with a numerical beach work very well in simulating wave propagation in water in a small computational domain.     

水下真空联合堆载预压处理潮间带软基

根据厦门岛西岸线整治工程B标段173m长岸线采用水下真空联合堆载预压处理软土地基的工程实例．介绍真空联合堆载预压在潮间带软基处理工程中的设计、施工、监测及加固效果。通过成功地应用水下真空联合堆载预压技术．并与同等的堆载预压加固方法进行比较．认为该方法具有施工工期短、软基强度增长快、地基沉降量小且造价低的优点．可供类似工程参考。     

轨道交通“捆绑式”开发的新模式

在分析地铁项目亏损的原因后,认为“捆绑式”开发已成为解决地铁可持续发展的必由之路。通过分析香港“地铁＋地产”的开发模式,提出香港模式有其成功所必须依赖的政策、法规、规划、地域等条件,这些条件是内地暂时无法具备也不能克隆的。根据广佛地铁的特点,尝试探索一条符合国情特征的捆绑式开发的新模式：“地铁＋地产＋产业园”。     

深水桥梁垫层隔震基础冲刷演化机理与设计建议

群桩和沉井作为跨江海桥梁的基础支撑体系已得到广泛应用,但近年来实际工程的水深不断增加,现有技术已难以适用于50 m以上的超深水环境条件。为研究垫层隔震基础这一新型深水桥梁基础的冲刷演化机理,针对周期为1.2 s,波高分别为4、6、8 cm的3种波浪条件,以及海流流速为25 cm·s^-1,波浪波高为6 cm,周期为1.2 s的波流共同作用条件,开展砂土中垫层隔震基础冲刷演化机理的波流水槽模型试验研究,结合仅单向流作用下的基础体系冲刷演化机制,重点考察并梳理了隔震垫层的5种典型破坏形式及其特点。结果表明：仅存在单向流作用时,垫层的破坏形式主要为边缘破坏、剪切破坏和完全破坏,且严重程度随流速增大而增大;存在波浪作用时,海床泥沙及垫层材料起动后将发生振荡,导致隔震垫层还会发生掩埋破坏和掏底破坏;波流共同作用时,产生的影响比二者单独作用时更严重,对基础体系的正常工作产生严重影响。此外,通过分析交界面位置附近材料在冲刷过程中的滑动与滚动过程,认为颗粒材料的滑动和滚动是造成隔震垫层材料流失的主要原因。最后,对比分析了国内外抛石设计规范中的粒径计算方法,并在此基础上对垫层材料的设计提出建议。     

组合式多机组交流传动互馈试验台研制

结合正在建设的组合式多机组交流传动互馈试验台,首先对试验台的基本原理、系统组成及试验功能进行介绍,接着对互馈试验台控制系统和测试系统进行分析和总结。该试验台具有组合方便、控制灵活、通用性强、高效节能等优点,能为高速动车组和机车交流传动系统及其部件的研发和试验提供条件。     

节点递归算法优化合流管网

根据合流制管网系统的图论和矩阵算法 ,提出节点递归优化算法 ,以节点为研究对象 ,优化合流制管网系统。本算法能解决管网在交汇点处上下游管段衔接计算问题、溢流井设置问题 ,克服控制点不易确定的困难 ,达到了费用最低的优化目标 ;并可直接以节点标高为约束条件 ,充分考虑利用原有管道或解决地下管线交叉问题。并通过实例进行了验证     

路段动态特征中的交通组成因素研究

基于对交通流建模过程中将车型单一考虑为标准小汽车,忽略了现实交通量中车型的不同构成,本文通过对不同车型的动力特性进行标定,将其特性反映在跟车模型与车道变换模型中,并且利用交通仿真技术,分析了交通量构成对路段行程时间、车速、延误等动态特性指标的影响。     

30kW微燃机电、热联供机组开发应用技术与经济分析

简单介绍了微燃机电、热联供机组工作原理，详细对比分析了工程实例与普通柴油发电机组及锅炉采暖技术与经济性能参数，对以后野外施工及偏远无市电地区能源保障提出了看法。     

悬索桥索鞍位置的分离计算法

关于索鞍位置计算,已有的计算方法较为繁琐或仅适用于单圆曲线索鞍,针对这种情况,将单圆曲线索鞍位置计算的分离计算法推广到复合圆曲线索鞍位置的计算中,从力学关系和几何关系出发推导得到了复合圆曲线索鞍位置计算的解析公式和由解析公式求解的牛顿-拉斐森迭代算法。改进约束条件,给出合理的迭代初值计算公式,确保了索鞍位置迭代计算快速收敛于真实解。归纳提出了理论顶点的顺延悬链线交点定义法和切线交点定义法的概念,探讨了两种定义法所得的索鞍位置计算公式或计算结果之间的必然联系。算例表明:该精确方法正确可行,近似方法也具有较高的精度,可供悬索桥施工、设计人员参考。