Implications of Thresholds in Discrete Choice Modelling

Abstract

Individual choices are affected by complex factors and the challenge consists of how to incorporate these factors in order to improve the realism of the modelling work. The presence of limits, cut‐offs or thresholds in the perception and appraisal of both attributes and alternatives is part of the complexity inherent to choice‐making behaviour. The paper considers the existence of thresholds in three contexts: inertia (habit or reluctance to change), minimum perceptible changes in attribute values, and as a mechanism for accepting or rejecting alternatives. It discusses the more relevant approaches in modelling these types of thresholds and analyses their implications in model estimation and forecasting using both synthetic and real databanks. It is clear from the analysis that if thresholds exist but are not considered, the estimated models will be biased and may produce significant errors in prediction. Fortunately, there are practical methods to attack this problem and some are demonstrated.     

Inclusion of latent variables in Mixed Logit models: Modelling and forecasting

Travel demand models typically use mainly objective modal attributes as explanatory variables. Nevertheless, it has been well known for many years that attitudes and perceptions also influence users’ behaviour. The use of hybrid discrete choice models constitutes a good alternative to incorporate the effect of subjective factors. We estimated hybrid models in a short-survey panel context for data among many alternatives. The paper analyses the results of applying these models to a real urban case study, and also proposes an approach to forecasting using these models. Our results show that hybrid models are clearly superior to even highly flexible traditional models that ignore the effect of subjective attitudes and perceptions.     

船体破损后非正浮条件下波浪载荷的计算方法

在船舶不沉性理论的基础上，采用符拉索夫法分析了不同破舱组合下的船体浮态参数。然后采用线性切片理论，计及水线以下破损后船舶由于舱室进水产生的横倾角与纵倾角的影响，利用多极展开法求解非对称剖面的二维辐射和绕射流场。计算了破损船体非正浮状态条件下的波浪载荷。在一定假定条件下，将切片法计算的波浪载荷同静置法计算结果进行了比较，分析了船体破损后的载荷变化。     

Effect of advanced traveler information systems and road pricing in a network with non-recurrent congestion

The effect of the application of advanced transport information system (ATIS) and road pricing is studied in a transportation system under non-recurrent congestion. A stochastic network deterministic user equilibrium model (SNDUE) with elastic demand is formulated and used to evaluate the welfare and private impacts of different market penetrations of ATIS, together with road pricing for a simple network. Both marginal first-best road pricing and a second-best fixed road pricing are considered. The incentives of private users to use ATIS are analyzed and the characteristics of optimum tolls as a function of ATIS market penetration are shown. We conclude that ATIS is an efficient and necessary tool to reduce the effects of non-recurrent incidents in a transportation network, especially when non-recurrent congestion causes a significant deterioration of operational conditions of the network. If the impact of non-recurrent incidents on free flow costs is small or is reduced only to congestion effects, the use of road pricing would be more efficient. Social benefits obtained when jointly implementing ATIS and road pricing are practically the same whether first-best or second-best road pricing is used. Considering the private costs perceived by the network users, and the benefits experienced by equipped users, the maximum level of market penetration achieved could be limited because private benefits disappear after certain market penetration is obtained.     

Tradeoffs in incremental changes towards pedestrian-friendly environments: Physical activity and pollution exposure

A microsimulation of individuals’ activities is used in the context of a risk analysis framework to assess the impacts of hypothesized changes to the built environment on personal energy expenditure and on inhalation of air pollutants. Uncertainty is assessed using Monte Carlo simulations and sensitivity analyzes. We find both simulated individuals that augment and others that reduce their energy expenditure and inhalation dose of pollutants, with median increases displaying larger magnitudes than the decreases. Up to 75% of the population has significant increases in energy expenditure and pollutant inhalation. We also find, however, high uncertainty associated with the estimates. Results differ considerably depending on the travel mode choice model used in the simulation.     

谈施工安全控制

分析了常见施工安全事故的特征及事故发生的原因，并结合多年的施工经验，介绍如何控制和保障施工安全的经验和体会。     

Quantitative analysis of passenger and baggage security screening at airports

The terrorist attacks in the United States in 2001 opened a new era in air transportation. The realization that civil aircraft can be used as powerful weapons of mass destruction by a small group of people has drastically increased the need for security screening procedures to protect civil flights. Serving as the interface between the air and land transportation modes, airports have become the main focus in the implementation of those procedures. The need to more thoroughly screen passengers and baggage, and the consequent increase in processing time, has created the need for more space for security checkpoints and baggage screening inside passenger terminal buildings—space that is costly and very difficult to find in existing buildings. This paper evaluates the impact those measures have had on the planning and operation of airport passenger terminals. Quantification of those impacts is performed with the use of discrete‐event simulation and spreadsheet models.     

Clustering and performance: the case of maritime clustering in The Netherlands

Over the last years, the concept of clustering has become a central concept for analysing the competitiveness of nations, industries and firms. The cluster concept can be usefully applied to study clustering of maritime activities. Maritime activities, such as shipping, shipbuilding and port and maritime services, are clearly geographically concentrated in a number of maritime clusters. Due to ongoing internationalization in these industries, the concentration of maritime activities in clusters is likely to increase. This observation leads to two important research questions: what are the advantages for firms to locate in clusters and what factors influence the development of maritime clusters? This study identifies four agglomeration economies that attract firms to cluster: a joint labour pool, a broad supplier and customer base, knowledge spillovers, and low transaction costs. Furthermore, it discusses the effects of aspects of the cluster structure, being the presence of internal competition, the heterogeneity of the cluster population, the entry and exit barriers, and the presence of (above mentioned) agglomeration effects. It also briefly discusses the important issue of cluster governance. This overview allows one to develop a theoretical framework to analyse clusters. In the empirical part, this framework is applied to the maritime cluster in The Netherlands. Based on empirical data, from surveys amongst firms in the maritime cluster, studies commissioned by the Dutch maritime Network and regional statistics, the presence of agglomeration economies in the cluster is shown. Secondly, it is shown that the cluster structure is beneficial for the performance. This paper finishes with conclusions and suggestions for further research.     

Baroclinic eddy formation in a Rhine plume model

A three-dimensional finite difference tidal model, including advective and diffusive transport of salinity, is used in the two-layer model for simulation of Rhine water outflow. Layer depths are adjusted in a way that no advective transports between upper and lower layer take place in case of sufficiently stable stratification.Model results show frontal eddy development related to (limited) growing internal waves in case of weak northeasterly to southeasterly winds. It is shown that baroclinically unstable conditions occur, related to vertical velocity shear, resulting in frontal meanders with wave lengths between 18 and 30 km. Satellite images of sea surface temperature show a comparable behaviour of the temperature front, which is strongly correlated with the salinity front of the Rhine plume.