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.     

杭州城市交通拥挤现状及对策

在分析杭州市交通供需现状的基础上,提出了规划多中心结构和混合功能区,以减少不必要的出行以及合理配置交通源,并对改善中心区交通提出切实可行的对策。     

Total cost analysis: An alternative to benefit-cost analysis in evaluating transportation alternatives

This paper explains the theory in support of total cost analysis (TCA) to compare transportation system alternatives. The full costs of each alternative are first aggregated, including travel time costs and monetizable environmental and social costs. Many costs which are considered on the benefits side of the equation in benefit-cost analysis (BCA) as "cost savings" are brought over to the costs side. Total cost differences among alternatives are then traded off against their estimated non-monetized benefits or impacts, just as a consumer trades off product quality against cost before deciding which product he or she will buy. One advantage of TCA over traditional BCA is that the concept of "total cost" is more easily understood by the public and by political decision-makers than BCA concepts such as "net present worth", "benefit-cost ratio" and "internal rate of return". A second advantage is that there is no suggestion that all "benefits" have been considered; decision-makers are free to use their own value judgements to trade off total cost against non-monetizable social, environmental and economic impacts, just as they trade off quality and convenience against cost when purchasing goods and services in their roles as consumers. The TCA approach is demonstrated in this paper through a case study of two systemwide alternatives for the Baltimore, MD urban area.     

喷锚支护的时间效应与空间效应

喷锚支护是新奥法构筑隧道的主要支护手段，为使喷锚支护与围岩形成共同承载结构，必须在适宜的时机及根据适当的围岩变位量来确定恰当的喷锚支护结构。     

一种基于排队长度的多入口匝道协调控制算法

匝道控制是一种限制交通流量,解决高速公路交通拥挤的有效手段。一种基于排队长度的多入口匝道协调控制的新型算法能根据不同的交通流采取不同的控制策略,从而更有效地控制入口匝道。采用Vissim仿真软件对该算法进行仿真,仿真结果验证了该算法的有效性。     

浅析深基坑分坑开挖对临近地铁附属结构的影响

以上海漕河泾开发区赵巷园区二期深基坑支护实例为背景,分析了邻近地铁深基坑工程的实际应用特点,介绍了基坑围护设计方案选型、分坑平面布置,以及考虑临近地铁的保护措施,基于有限元数值模拟归纳,分析了分坑的空间平面尺寸对临近地铁附属结构变形的影响,并通过有限元分析结果与基坑实际设计方案进行对比。结果表明,控制临近地铁基坑的分坑宽度在2倍的基坑挖深左右,可以有效控制基坑开挖对邻近建筑的变形速率和总变形影响。     

基于排队论的湛江港湾内锚地总体布局分析

针对湛江港湾内船舶密度大、种类多、大小各异以及锚位供不应求的情况,为科学规划锚地,通过实地调研湛江港锚泊需求和锚地运行状况,在锚位等级划分的基础上,利用排队论方法建立湛江港湾内最佳锚位数的计算模型,并基于测算出的锚位需求提出近期和远期锚地规划方案。相比于不做锚位等级划分而单一计算锚位数的做法,得出的湛江港湾内锚泊需求更符合实际,锚地位置布局更合理、功能划分更完善、锚泊安全更有保障,可以减少锚地过度建设造成的资金浪费,具有显著的社会经济效益。     

UUV航迹跟踪的双闭环Terminal滑模控制

针对模型参数不确定及存在外界海流扰动情况下全驱型无人水下航行器(UUV)的航迹跟踪问题,提出了一种双闭环Terminal滑模控制方法。首先,为了防止UUV位置和姿态跟踪控制出现超调量过大的问题,在外环中引入位置和姿态负反馈,设计了UUV的参考速度作为镇定UUV位置和姿态跟踪误差的虚拟控制律。然后,在内环中将虚拟控制律作为跟踪目标。考虑到传统滑模控制会出现“抖振”现象,采用Terminal滑模控制方法,在消除“抖振”的同时,使滑模面上的速度跟踪误差在有限时间内收敛到稳态。最后,运用Lyapunov稳定性理论证明了该双闭环Terminal滑模控制系统的稳定性。仿真结果表明,该控制方法能够实现UUV对空间航迹的精确跟踪。     

基于闭排队网络的弹射器数量配置方法

弹射器配置数量对舰载机出动回收能力有很大影响,因此,在航母设计初期多方案论证阶段,弹射器的数量配置是必须考虑的关键问题之一。针对舰载机起飞过程的排队特点以及整个出动回收过程的闭环特点,基于排队理论建立舰载机出动回收过程的闭排队网络模型,分析弹射器数量对出动回收能力的影响,分析结果可用于支撑弹射器的数量配置设计方案。为验证模型的有效性,采用\     

高速公路车辆排队尾部交通事故时空分布特征

根据高速公路常发拥堵路段的交通流数据, 采用累计占有率法绘制交通流占有率波动曲线, 用来判断拥堵路段内车辆排队尾部轨迹, 分析了占有率、里程位置、时间间隔的关系, 确定了累计占有率曲线的拐点。分析了排队传播、消散过程中交通事故频数与时间、空间距离的关系, 对分布特征进行了统计分析。分析结果表明: 车辆在时间和空间上接近排队车辆尾部时, 发生交通事故的频数明显增加, 时间距离与空间距离以排队尾部为中心呈现正态分布, 不同行驶方向路段内正态分布曲线不存在显著差异, 但拥堵传播与消散过程的正态分布曲线存在显著差异。建立的事故发生概率的联合正态分布模型, 可用于预测排队车辆尾部附近的交通事故风险, 为实施动态交通控制以提高快速道路交通安全提供理论依据。