Using the Bayesian updating approach to improve the spatial and temporal transferability of real-time crash risk prediction models

This study aimed to improve the spatial and temporal transferability of the real-time crash risk prediction models by using the Bayesian updating approach. Data from California’s I-880N freeway in 2002 and 2009 and the I-5N freeway in 2009 were used. The crash risk models for these three datasets are quite different from each other. The model parameters do not remain stable over time or space. The transferability evaluation results show that the crash risk models cannot be directly transferred across time and space. The updating results indicate that the Bayesian updating approach is effective in improving both spatial and temporal transferability even when new data are limited. The predictive performance of the updated model increases with an increase in the sample size of the new data. In addition, when limited new data are available, updating an existing model is better than developing a model using the limited new data.     

Modelling major traffic incident impacts and estimation of their associated costs

Network area-wide impacts due to major traffic incidents can be assessed using a microsimulation approach. A VISSIM microsimulation model for a motorway network has been developed and is used to quantify impacts of a major incident in terms of associated costs. The modelled results reveal that a 65% capacity reduction results in 36% more incident-induced delay when compared with the application of a 50% capacity reduction assumption for a two-hour incident clearance duration that blocked one lane of a two-lane motorway. Additionally, an incident which caused a full blockage incurred 40 times more associated impact costs when compared with a major incident which caused a one lane blockage. A 23% cost saving can be achieved by clearing one lane of a fully blocked two-hour major traffic incident after 90 minutes, while a 37% cost saving can be achieved by clearing all blockages after 90 minutes.     

空间分析方法在航线设计和航路监视中的应用

探讨在电子海图中，使用GIS空间分析函数自动判断计划航线的偏航极限范围内是否存在危险点、线、面的方法，为航线设计起决策参考，在航行过程中，起实时航路监视作用。     

Spatial and temporal variation of bacterioplankton in a sub-Antarctic coastal area (Kerguelen Archipelago)

Bacterial abundance and production were measured monthly for one year along cross-shore transects in 3 sub-Antarctic fjords of the Kerguelen Archipelago (seven stations each). Mean values of the 3 most coastal (inside) and most offshore (outside) stations were used to describe the relationship between temperature, phytoplankton biomass, bacterial abundance and bacterial production over a one year annual cycle. The entire sampling protocol was repeated twice during each cruise: once at noon and once at midnight. Over the whole sampling period, the temperature ranged from 2.1 to 7.4 °C, while chlorophyll a concentrations varied by a factor of 10, and bacterial abundance and production varied by factors of 12 and 30, respectively. Within one day, all of these parameters sometimes varied by a factor of 4 between noon and midnight. A clear seasonality was observed for all of the parameters. However, while variations of phytoplankton and bacterial production paralleled those of temperature, bacterial abundance was low in midsummer and maximum in autumn. While no general pattern could be observed from the total data set, spatial gradients could interfere strongly with temporal changes.     

京沪高速铁路(京徐段)跨线桥梁设计概述

京沪高速铁路(京徐段)多次跨越既有铁路,跨越既有线桥涵设计是京沪高速铁路桥梁设计的重要节点。通过对上跨大李联络线及预留复线、京山四线及西黄左线、两个津浦单线、津浦双线等四处跨线桥梁工点介绍,针对不同的既有线现状情况,总结出跨越既有线桥涵设计的常用结构形式为:空间刚架、悬浇连续梁、基础斜置简支梁及转体施工连续梁。     

LBS空间数据内容与管理方法

LBS空间数据的管理和数据库建立是LBS定位服务系统的核心。本文在论述了LBS系统各个部分的构成的基础上,探讨了LBS空间数据库管理的具体内容,设计了基于Oracle Spatial对象关系型数据库的LBS空间数据存储与管理的方法,设计和开发了面向对象的空间数据引擎,研究了LBS数据通过空间数据引擎上传到Oracle Spatial的技术。     

A multi-layer scenario analysis for sustainable international transport

This article considers the development of the international transport sector based on four globalization scenarios. These four images of the future transportation market are constructed at three different levels (global, European and Dutch). The possible consequences of these scenarios are mapped out not only by key aspects such as modal split and spatial organization but also by providing empirical insights into expected transport flows for both passenger and freight transport in 2020 based on data from 1995.     

Measurements and statistical analysis of fillet weld geometrical parameters for probabilistic modelling of the fatigue capacity

Welded joints are commonly used for various structures such as civil engineering infrastructures or marine and submarine structures. It is well known that the geometry of the joints has an important influence on the stress concentration factor and thus on fatigue lifetime. Non-Destructive controls during welding work allow to keep parameters inside bounds and to satisfy quality requirements. However, the effect of the geometry characteristics within these bounds on the structural lifetime needs for a statistical analysis and a probabilistic modelling on the one hand and for a specific computational method on the other hand. When considering the first point, only few works have been carried out on the statistical analysis of the geometrical parameters of a welded joint. The measurement of the different parameters of this geometry is a long and scrupulous work. Recently, some laser process allows obtaining a significant quantity of trajectories along a welded joint for these geometrical parameters. This paper aims at analysing these trajectories for reliability purpose. This laser process allowed us to measure the width of the weld, the angle at the junction between weld and welded component and the radius at the weld toe. The study was completely performed for the two first but it was shown that the assessment of the radius remains challenging.     

The maximum approximate composite marginal likelihood (MACML) estimation of multinomial probit-based unordered response choice models

The likelihood functions of multinomial probit (MNP)-based choice models entail the evaluation of analytically-intractable integrals. As a result, such models are usually estimated using maximum simulated likelihood (MSL) techniques. Unfortunately, for many practical situations, the computational cost to ensure good asymptotic MSL estimator properties can be prohibitive and practically infeasible as the number of dimensions of integration rises. In this paper, we introduce a maximum approximate composite marginal likelihood (MACML) estimation approach for MNP models that can be applied using simple optimization software for likelihood estimation. It also represents a conceptually and pedagogically simpler procedure relative to simulation techniques, and has the advantage of substantial computational time efficiency relative to the MSL approach. The paper provides a “blueprint” for the MACML estimation for a wide variety of MNP models.     

A coupled multi-agent microsimulation of social interactions and transportation behavior

Choice set formation, location and mode preferences, coordinated scheduling, alternative utility valuations, and shared mobility resources are among the many activity-travel issues hypothesized to be significantly influenced by traveler interdependencies. Empirical evidence lags theory, particularly about the geography of social networks. A simulation tool is presented to let the experimenter construct and test hypothetical interdependencies between geography, socially-linked travelers, and activity-travel choices. The exploratory tool is integrated in the Multi-Agent Transportation Simulation Toolbox (MatSim-T). Initially, any social network can be constructed and embedded in geography. It can remain static, or be adapted to the travel patterns of the agents. The interactions and exchanges between agents influencing socializing and/or travel behavior can be defined in substance and in time/space. The reward for socializing or being socially linked can be varied. Finally, the co-dependence of social factors and travel behavior can be studied. This paper introduces the model and presents verification results which illustrate the coupling of extremely simplified socializing assumptions and travel behavior.