Transport Modeling

A colloid transport model is introduced that is conceptually simple yet captures the essential features of colloid transport and retention in saturated porous media when colloid retention is dominated by the secondary minimum because an electrostatic barrier inhibits substantial deposition in the primary minimum. This model is based on conventional colloid filtration theory (CFT) but eliminates the empirical concept of attachment efficiency. The colloid deposition rate is computed directly from CFT by assuming all predicted interceptions of colloids by collectors result in at least temporary deposition in the secondary minimum. Also, a new paradigm for colloid re-entrainment based on colloid population heterogeneity is introduced. To accomplish this, the initial colloid population is divided into two fractions. One fraction, by virtue of physiochemical characteristics (e.g., size and charge), will always be re-entrained after capture in a secondary minimum. The remaining fraction of colloids, again as a result of physiochemical characteristics, will be retained “irreversibly” when captured by a secondary minimum. Assuming the dispersion coefficient can be estimated from tracer behavior, this model has only two fitting parameters: (1) the fraction of the initial colloid population that will be retained “irreversibly” upon interception by a secondary minimum, and (2) the rate at which reversibly retained colloids leave the secondary minimum. These two parameters were correlated to the depth of the Derjaguin-Landau-Verwey-Overbeek (DLVO) secondary energy minimum and pore water velocity, two physical forces that influence colloid transport. Given this correlation, the model serves as a heuristic tool for exploring the influence of physical parameters such as surface potential and fluid velocity on colloid transport.

Calibration and validation of dynamic assignment models to simulate urban road transport systems in ordinary conditions are still an open issue. This problem is further emphasized in the case of transport systems analysis in emergency conditions, as there are no standardised methods and there is a lack of experience of real-world applications. The paper presents a DA model and a procedure able to simulate transport supply and transport supply – travel demand interaction of an urban road transport system in emergency conditions. The transport supply models are calibrated and validated through traffic data observed during a real-world evacuation experiment conducted in the town of Melito di Porto Salvo (Italy). The DA model has been applied in order to reproduce the observed real-world evacuation experiment and a set of indicators for testing the performance of a road network in emergency conditions is estimated. We think that the findings reported in the paper represent a contribution in the field of transportation systems analysis in emergency conditions at urban scale. The specified and calibrated DA model and the applied set of indicators can be a useful tool to support the planning and management of road networks and mobility in emergency conditions.

"The usability of the Taguchi method in traffic simulation was investigated to demonstrate whether full factorial
scenario testing is necessary on a small road network by changing certain links into one-way streets to ascertain the
minimum total delay. A network with 52 links was constructed and four arbitrarily chosen links were made one-way
streets, one by one in both directions. The best directions of traffic for each of these four links which gave minimum
total delay time over the whole network were studied by means of Paramics microsimulation software. The
simulation runs were designed using an orthogonal array technique in L8 array with four factors (with two levels
each) and three interactions. The total delay time was selected as the response variable. The response data were
analysed using an analysis of variance technique by the Taguchi method. In addition, the Taguchi outcome was
judged against the results of the full factorial design of the actual Paramics runs for the best and transparent
comparison. Furthermore, in comparison with full factorial design, the results demonstrated that the use of the
Taguchi method enabled the interactions between the factors to be seen, which cannot be achieved so simply by
simulation trials."

"Earlier work by the author developed a two-dimensional
car-following model by taking into account the lateral
discomfort experienced between the neighbouring vehicles
moving in the same direction. This incorporation of lateral
friction in car-following theory may offer a potential
breakthrough in the field of microscopic simulation.
However, that model was based on a small-scale scrutiny in
which the interactions between only two or three vehicles
were analysed in isolation. The treatment of the problem
with many vehicles in a stream of traffic, say, on a link, was
not made. The present paper, therefore, develops a
simulation model with various types of vehicular
interactions, including lane changing, and performs certain
verification checks. The results show that the simulation
behaves rationally giving credibility to the approach
introduced. Although a number of comparisons with
empirical observations are made in the paper, complete
validation and experimentation are left for further work.
Furthermore, the paper draws research attention to the
area so that various existing car-following models can be
modified in a similar way to mimic non-lane-based car
following in multilane traffic flow. Potential practical
implication of the work for traffic engineers is mainly
capacity assessments especially in places where the
discipline of lane-based-driving is weak."

Project promoters, forecasters, and managers sometimes object to two things in measuring inaccuracy in travel demand forecasting: (1) using the forecast made at the time of making the decision to build as the basis for measuring inaccuracy and (2) using traffic during the first year of operations as the basis for measurement. This paper presents the case against both objections. First, if one is interested in learning whether decisions about building transport infrastructure are based on reliable information, then it is exactly the traffic forecasted at the time of making the decision to build that is of interest. Second, although ideally studies should take into account so-called demand “ramp up” over a period of years, the empirical evidence and practical considerations do not support this ideal requirement, at least not for large-N studies. Finally, the paper argues that large samples of inaccuracy in travel demand forecasts are likely to be conservatively biased, i.e., accuracy in travel demand forecasts estimated from such samples would likely be higher than accuracy in travel demand forecasts in the project population. This bias must be taken into account when interpreting the results from statistical analyses of inaccuracy in travel demand forecasting.

This paper presents a methodology to evaluate rail-road freight policies such as new services and/or incentives for long- distance freight transport by using a mixed what-if/what-to approach. It uses a specific mode-service choice model to share the freight demand among alternatives (rail-road combined transport, maritime Ro-Ro and road transport) and a service network design model to identify new rail-road freight services. This methodology is designed to be easily integrated within a Decision Support System to allocate the freight transport policies. Finally, in order to show the applicability of the proposed approach, some application examples carried out to support Italian Ministry of Transport in the development of the new Italian National Transport Plan are presented.

""Today, the worlwide communities have to deal with the large number of road vehicles while preserving the economic sustainability and, at the same time, the environmental quality.
Following the Kyoto Protocol many policies have been implemented in order to reduce the negative effects of pollutant emissions. Many of them refer to transpor-tation sector. In Italy, they have been implemented without ex-ante assessment of the impacts and will not be effective. In the paper, an ex-ante assessment method-ology of transport policies, with a focus on the assessment of pollutant emissions, has been proposed. The proposed methodology for road emission is based on quantitative methods and models. It allows a more accurate estimation of transportation attributes used in the forecasting analysis of road emissions.
The methodology was applied to the Italian context in realtion to two scena-rios: short and medium-long terms. Useful indications in terms of policy making could be derived. All policies that will be implemented in the next future produce, in the short term scenario, a reduction of pollutant emissions, but in the long term scenario they will not be enoght. Further policies are required to meet the targets of Kyoto Protocol, as well as: addressing demand to low carbon fuel, promotion of optimization and grouping private road transport, construction of new transportation infrastructures and expansion of existing ones, promotion of environmental-friendly transportation modes, promotion of Intelligent Transportation Systems (ITS), editing of Transportation Plans.""

The paper focuses on choices for restocking retailers and food-and-drink outlets. It aims at identifying the main variables affecting the strategy, the transport service and distributor types for restocking, such as the characteristics of shop (e.g. number of employees) and deliveries (e.g. frequency, time, freight type, quantity). Models for the simulation of vehicle type choice made by retailer on own account are also presented and the effects due to his socio-economic characteristics and available vehicles.

This paper is focus on the calibration in the OD pair and the link cost functions for road freight truck are specified and calibrated for different categories. Three main categories are individuated: freeways, extra-urban roads and other types.

Megaproject Planning and Management: Essential Readings contains the seminal articles from the growing body of research on megaproject planning and management along with an original introduction by the editor, Bent Flyvbjerg. The leading and most cited authority in the field, Flyvbjerg has used crowdsourcing and 25 years of experience to cherry-pick from several hundred articles and books the writings that define the field. This volume will be an indispensable source for those wishing to speak with authority about how megaprojects are prepared, delivered, and fought over. The target audience is students, academics, practitioners, and media pundits alike, as well as communities affected by megaprojects.

Travel time saving plays an important role in the socio-economic studies of the profitability of transport projects. This paper presents some parts of our studies performed in collaboration with SETRA (French Ministry of Transport) on the economic evaluation of operating roads. The present paper includes four main parts. In the first section, we describe how the decisions of travelers are influenced by the variability of travel time. The statistical analysis of the recorded travel time on a motorway in Île-de-France is developed to quantify the variability of travel time and to measure its magnitude. The second section is devoted to developing the methodological framework to capture the safety margin considered by travelers in their trip making behaviors. A model is formulated to reflect the behavior of the traveler before making a trip. This model highlights the effect of each travel component, the mean of the travel time, the level of variability, and the safety margin taken by the traveler before traveling. The third section extracts the optimal safety margin that minimizes the cost of the total time allocated to travel. Finally, the last section of this paper is devoted to some algebraic manipulation in order to characterize the features of the output if the variability of travel time in the economic evaluation of transport projects is incorporated. An expression is also provided for the gain brought by operators when they reduce the variability of travel time or they reduce the uncertainty felt by travelers through providing information to them.

For over fifty years, successive waves of critique have underscored that the apolitical character of much of Political Science research betrays the founding mission of the discipline to have science serve democracy. The Caucus for a New Political Science was originally based on such a critique, and the Perestroika movement in the discipline included a call for more problem-driven as opposed to theory- or method-driven work that would better connect Political Science research to ongoing political struggles. In recent years, movements for a public Sociology and public Anthropology as well as dissonant movements in Economics and related fields have added to the insistence that social science research was too often disconnected from the real world. Phronetic Social Science has emerged out of the ferment for change in the social sciences, starting with the much-debated book by Bent Flyvbjerg, Making Social Science Matter (Cambridge 2001). Flyvbjerg critiqued the social sciences for mimicking the natural sciences while proposing an alternative approach that focuses research on helping people address the problems they are facing in the context they are facing them. Today, Phronetic Social Science goes beyond the call for an alternative approach to social inquiry and its growing adherents are providing evidence that this alternative approach to doing research can enrich the social sciences by more effectively connecting research to efforts to address real world problems as people experience them. This essay provides a genealogy of efforts to connect Political Science to politics, a review of the major critiques of mainstream research, an explication of the rationale for more problem-driven, mixed methods research, a specification of the key principles of the phronetic approach, and examples of its application in the public realm. The essay concludes with implications for realizing a more political Political Science by way of taking a phronetic approach.

Abstract: Road congestion is increasing due to growing of the population and vehicle ownership. Due to this problem there is a need of the advanced traveller information system in optimizing the traffic in urban area. In Malaysia the rapid increase in the use of personal transport has resulted in increased traffic congestion, accidents, inadequate parking space and air pollution, among other problems.

Abstract: Libya is a rich developing country which suffers the consequences of explosions in both human and motorization. This has been accompanied by a heavy toll of deaths and economic cost. Road accidents were the cause of I0% of all deaths. Therefore, this research foresee in contributing greater extra details on car users mode choice behavior to better understand the likely measures that would have to be taken to encourage greater public transport use.

This article addresses three main issues. First, it argues that David Laitin, in a misguided critique of Bent Flyvbjerg’s book Making Social Science Matter for being a surrogate manifesto for Perestroika, misrepresents the book in the extreme. Second, the article argues that Laitin’s claim that political science may become normal, predictive science in the natural science sense is unfounded; the claim is a dead end that perestroikans try to get beyond. Finally, the article proposes that political scientists substitute phronesis for episteme and thereby avoid the trap of emulating natural science. By doing so, political scientists may arrive at social science that is strong where natural science is weak: in the reflexive analysis and discussion of values and interests aimed at praxis, which is the prerequisite for an enlightened political, economic, and cultural development in any society.

Understanding travel behaviour and travel demand is of constant importance to transportation communities and agencies in every country. Nowadays, attempts have been made to automatically infer transportation modes from positional data, such as the data collected by using GPS devices so that the cost in time and budget of conventional travel diary survey could be significantly reduced. Some limitations, however, exist in the literature, in aspects of data collection (sample size selected, duration of study, granularity of data), selection of variables (or combination of variables), and method of inference (the number of transportation modes to be used in the learning). This paper therefore, attempts to fully understand these aspects in the process of inference. We aim to solve a classification problem of GPS data into different transportation modes (car, walk, cycle, underground, train and bus). We first study the variables that could contribute positively to this classification, and statistically quantify their discriminatory power. We then introduce a novel approach to carry out this inference using a framework based on Support Vector Machines (SVMs) classification. The framework was tested using coarse-grained GPS data, which has been avoided in previous studies, achieving a promising accuracy of 88% with a Kappa statistic reflecting almost perfect agreement.

"Growing demands for forest products and services, accentuated by political goals of increased utilisation of renewable resources imply that pressure on mountain forests is likely to intensify considerably in the future. This increased demand will be met with human innovation. However, the economic marginality of forest operations in steep terrain, together with their isolated location, make mountain forests particularly vulnerable to management practices with little scientific basis.  This conference aims to reiterate the existence and expansion of a scientific community that can lead the forest sector, and society at large, along the path of sustainable utilisation of this valued forest resource.     

Call for papers
We encourage the submission of abstracts including a strong element of steep terrain operations by Jan. 12th 2013 within one of the following thematic areas:
1. Planning  or monitoring (access-, operations-, environmental planning )
2. Steep terrain operations (roads, silviculture, harvesting,  transport): techniques, machines, systems
3. Business: costing, economics, logistics
4. The human factor: recruiting, training, ergonomics, safety
5. Avoidance or mitigation of environmental or social impacts and influences
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