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See detailCalibration of MATSim in the context of natural hazards in Liège (Belgium): Preliminary results
Saadi, Ismaïl ULiege; El Saeid Mustafa, Ahmed Mohamed ULiege; Teller, Jacques ULiege et al

in Proceedings of the 12th Conference on Transport Engineering (2016)

In Belgium, river floods are among the most frequent natural disasters and they may cause important changes on travel demand. In this regard, we propose to set up a large scale scenario using MATSim for ... [more ▼]

In Belgium, river floods are among the most frequent natural disasters and they may cause important changes on travel demand. In this regard, we propose to set up a large scale scenario using MATSim for guarantying an accurate assessment of the river floods impact on the transportation systems. In terms of inputs, agent-based models require a base year population. In this context, a synthetic population with a respective set of attributes is generated as a key input. Afterwards, agents are assigned activity chains through an activity-based generation process. Finally, the synthetic population and the transportation network are integrated into the dynamic traffic assignment simulator, i.e. MATSim. With respect to data, households travel surveys are the main inputs for synthesizing the populations. Besides, a steady-state inundation map is integrated within MATSim for simulating river floods. To our knowledge, very few studies have focused on how river floods affect transportation systems. In this regard, this research will undoubtedly provide new insights in term of methodology and traffic pattern analysis under disruptions, especially with regard to spatial scale effects. The results indicate that at the municipality level, it is possible to capture the effects of disruptions on travel behavior. In this context, further disaggregation is needed in future studies for identifying to what extent results are sensitive to disaggregation. In addition, results also suggest that the target sub-population exposed to flood risk should be isolated from the rest of the travel demand to reach have more sensitive effects. [less ▲]

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See detailA framework to identify housing location patterns using profile Hidden Markov Models
Saadi, Ismaïl ULiege; Liu, Feng; El Saeid Mustafa, Ahmed Mohamed ULiege et al

in Advanced Science Letters (2016), 22(9), 2117-2121

The determination of comprehensive activity-travel patterns is important in the context of agent-based micro-simulation modelling. This paper presents an improved method based on profile Hidden Markov ... [more ▼]

The determination of comprehensive activity-travel patterns is important in the context of agent-based micro-simulation modelling. This paper presents an improved method based on profile Hidden Markov Models (pHMMs) able to include information related to the agents’ residential locations. As proposed in the framework of Liu et al. (2015), pHMMs only characterize activity-travel patterns from the activity sequences perspective. In this context, information related to the primary activity locations (e.g. home, work) is not available and, as a result, it cannot be extracted from the pHMMs themselves. With respect to this limitation, we propose to apply the framework of Liu et al. (2015) with an extension to include characterization of residential locations. Following the established guidelines, the activity sequences and their related residential locations are extracted from the activity-travel diaries in order to estimate the regularity of the activities as well as their sequential order. Subsequently, within each residential activity, we include a categorization at an aggregate level (provinces). The methodology is powerful as it characterizes any length of sequence, allowing the generation of unlimited agent plans with information about residential location. Regarding data collection, the activity-travel diaries are provided by the Belgian Household Daily Travel Survey (2010). The results obtained after the simulations indicate a good match between the predicted and observed residential locations at both the national and provincial levels. [less ▲]

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See detailBelgium: The Use of MATSim within an Estimation Framework for Assessing Economic Impacts of River Floods
Saadi, Ismaïl ULiege; Teller, Jacques ULiege; Cools, Mario ULiege

in Horni, Andreas; Nagel, Kai; Axhausen, Kay W. (Eds.) The Multi-Agent Transport Simulation MATSim (2016)

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See detailModelling children’s mobility and school commuting: a review and key challenges for further research
Marique, Anne-Françoise ULiege; Teller, Jacques ULiege; Cools, Mario ULiege

Poster (2016)

Children’s mobility and school travelling are relatively underdeveloped in transport research, especially when compared with commuting to work. Despite it is often argued that a profound analysis of ... [more ▼]

Children’s mobility and school travelling are relatively underdeveloped in transport research, especially when compared with commuting to work. Despite it is often argued that a profound analysis of school-travel patterns has the potential to generate many important insights that may impact transport-system policy and management, the modelling of children mobility, is still in an early stage of development and children are often only considered as constraints to adults’ mobility. In this paper, we argue that innovative modelling frameworks that were recently developed in the field of transportation could be adapted and applied to the mobility of children in order to develop both novel scientific insights and inform the development of policies aiming at increasing active and independent mobility of children, in a broader vision of sustainability. [less ▲]

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See detailLogistics Service Quality: The Case of Da Nang City
Limbourg, Sabine ULiege; Giang, Ho Thi Quynh; Cools, Mario ULiege

in Procedia Engineering (2016), 142

Cost minimization is a key objective in managing logistics services. In this context, a growing interest in quality improvement can be observed. However, service quality is hard to quantify as it is a ... [more ▼]

Cost minimization is a key objective in managing logistics services. In this context, a growing interest in quality improvement can be observed. However, service quality is hard to quantify as it is a function of varying customer perceptions over time, of the measurement process and of the analysis of the data gathered. This study examines the logistics service quality by scales developed according to SERVQUAL instrument. A survey of 200 customers of logistics service providers (LSP) was conducted in Da Nang City. The data analysis shows that LSPs in Da Nang city need to improve Research and Development and to develop Customer Care programs. [less ▲]

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See detailBi-objective Road and Pipe Network Design for Crude Oil Transport in the Sfax Region in Tunisia
Belaid, Emna ULiege; Limbourg, Sabine ULiege; Mostert, Martine ULiege et al

in Procedia Engineering (2016), 142

In this paper, we examine a bi-objective road and pipe network design for crude oil transport in the Sfax region in Tunisia. In particular, we search for the minimum spanning trees (MST) that connect the ... [more ▼]

In this paper, we examine a bi-objective road and pipe network design for crude oil transport in the Sfax region in Tunisia. In particular, we search for the minimum spanning trees (MST) that connect the different oil fields with the port of La Skhirra. In the determination of the minimum spanning trees, two objectives are taken into account, i.e. accident risk and construction costs. By using an improved ɛ-constraint resolution technique, the Pareto optimal combinations of risk and cost are found. Results indicate that the network solutions by pipe outperform the solutions by road. When the minimum spanning trees for the two extremes on the Pareto curves, i.e. the cost minimum and risk minimum, are compared, one could note considerable differences in the links that form the MST. This implies that policy makers have an important role in deliberating between costs and risks. [less ▲]

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See detailUne analyse dynamique des interactions entre acteurs portuaires et leurs effets sur l’efficience d’un port pétrolier
Belaid, Emna ULiege; Rigo, Philippe ULiege; Cools, Mario ULiege

in Recueil des articles des 34èmes Rencontres Universitaires de Génie Civil de l'AUGC (2016)

The port is a heterogeneous entity which includes a set of actors whose objectives are sometimes contradictory. The analysis of their interactions allows us to understand the mechanism that governs the ... [more ▼]

The port is a heterogeneous entity which includes a set of actors whose objectives are sometimes contradictory. The analysis of their interactions allows us to understand the mechanism that governs the port management. This mechanism influences the port performance. In this article, we analyze port efficiency as a dynamic model. The latter is based on a framework established by a systemic analysis. From the simulations performed, it may be concluded that the parameters "loading rate" and "Connector dimension" are the most important parameters. Investment in new facilities for the port of La Skhira (Sfax, Tunisia) is our main recommendation. [less ▲]

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See detailIterative Proportional Fitting to expand a synthetic sample into a synthetic population
Cools, Mario ULiege

Scientific conference (2016)

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See detailÉvaluation des impacts économiques indirects selon un scénario de risque d’inondation
Saadi, Ismaïl ULiege; El Saeid Mustafa, Ahmed Mohamed ULiege; Teller, Jacques ULiege et al

in Recueil des articles des 34èmes Rencontres Universitaires de Génie Civil de l'AUGC (2016)

In this paper, we propose an integrated framework to estimate the indirect economic impact due to flood risk in Belgium. By taking into account the land-use change and different scenarios of climate ... [more ▼]

In this paper, we propose an integrated framework to estimate the indirect economic impact due to flood risk in Belgium. By taking into account the land-use change and different scenarios of climate change, the economic impact can be estimated at the micro-scale level using an Input-Output (I-O) approach. I-O is an econometric model that represents the structure of an economy in the form of a Production-Consumption (P-C) matrix. From a physical point of view, it corresponds to commodity flows between different sectors classified according to the NACE code. This approach is implemented to describe and to better understand the propagation of higher order damage through the entire economic structure. This tool can be used to take strategic decisions in the case of transport and land-use policies within vulnerable areas. [less ▲]

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See detailHidden Markov Model-based population synthesis
Saadi, Ismaïl ULiege; El Saeid Mustafa, Ahmed Mohamed ULiege; Teller, Jacques ULiege et al

in Transportation Research. Part B : Methodological (2016), 90

Micro-simulation travel demand and land use models require a synthetic population, which consists of a set of agents characterized by demographic and socio-economic attributes. Two main families of ... [more ▼]

Micro-simulation travel demand and land use models require a synthetic population, which consists of a set of agents characterized by demographic and socio-economic attributes. Two main families of population synthesis techniques can be distinguished: (a) fitting methods (iterative proportional fitting, updating) and (b) combinatorial optimization methods. During the last few years, a third outperforming family of population synthesis procedures has emerged, i.e., Markov process-based methods such as Monte Carlo Markov Chain (MCMC) simulations. In this paper, an extended Hidden Markov Model (HMM)-based approach is presented, which can serve as a better alternative than the existing methods. The approach is characterized by a great flexibility and efficiency in terms of data preparation and model training. The HMM is able to reproduce the structural configuration of a given population from an unlimited number of micro-samples and a marginal distribution. Only one marginal distribution of the considered population can be used as a boundary condition to “guide” the synthesis of the whole population. Model training and testing are performed using the Survey on the Workforce of 2013 and the Belgian National Household Travel Survey of 2010. Results indicate that the HMM method captures the complete heterogeneity of the micro-data contrary to standard fitting approaches. The method provides accurate results as it is able to reproduce the marginal distributions and their corresponding multivariate joint distributions with an acceptable error rate (i.e., SRSME=0.54 for 6 synthesized attributes). Furthermore, the HMM outperforms IPF for small sample sizes, even though the amount of input data is less than that for IPF. Finally, simulations show that the HMM can merge information provided by multiple data sources to allow good population estimates. [less ▲]

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See detailFree public transport: A socio-cognitive analysis
Cools, Mario ULiege; Fabbro, Yannick; Bellemans, Tom

in Transportation Research. Part A : Policy & Practice (2016), 86

In this study, the modal shift potential of introducing a free alternative (free public transportation) and of changing the relative prices of transportation is examined. The influence of a cognitive ... [more ▼]

In this study, the modal shift potential of introducing a free alternative (free public transportation) and of changing the relative prices of transportation is examined. The influence of a cognitive analysis on the zero-price effect is also analyzed. The data used for the analysis stem from a stated preference survey with a sample of approximately 670 respondents that was conducted in Flanders, Belgium. The data are analyzed using a mixed logit model. The modeling results yield findings that confirm the existence of a zero-price effect in transport, which is in line with the literature. This zero-price effect is increased by the forced cognitive analysis for shopping trips, although not for work/school or recreational trips. The results also demonstrate the importance of the current mode choice in hypothetical mode choices and the importance of car availability. The influence of changing relative prices on the modal shift is found to be insignificant. This might be partially because the price differences were too small to matter. Hence, an increase in public transport use can be facilitated by the introduction of free public transport, particularly when individuals evaluate the different alternatives in a more cognitive manner. These findings should be useful to policy makers evaluating free public transport and considering how best to target and promote relevant policy. [less ▲]

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See detailIdentifying mismatch between urban travel demand and transport network services using GPS data: A case study in the fast growing Chinese city of Harbin
Cui, JianXun; Liu, Feng; Hu, Jia et al

in Neurocomputing (2016), 181

The world's urban population growth and economic development have led to the reshaping of metropolitan space layouts among residential, employment and shopping locations, generating growing mismatch ... [more ▼]

The world's urban population growth and economic development have led to the reshaping of metropolitan space layouts among residential, employment and shopping locations, generating growing mismatch between travel demand and transport services. A reliable method to accurately analyze mobility demand and underlying transport network systems and to identify areas with serious mismatch problems is important for the design of effective policy measures. In this paper, we make use of the wide deployment of GPS devices in vehicles in many cities today, to develop such a method. This approach is developed using GPS data collected from all taxis operating in the Chinese city of Harbin between July and September in 2013. It consists of four major steps. First, city-wide mobility patterns are modeled based on GPS trajectories. This model captures a set of key traffic characteristics for each pair of regions in the entire urban network, including travel demand, travel speed and route directness of travel paths. From this model, a set of indicators is then built to measure the road transport performance between the regions, and the areas with serious mismatch problems are subsequently pinpointed. Finally, the identified problematic regions are further examined and specific transport problems are analyzed. By applying the proposed method to the city of Harbin, the potential and effectiveness of this method are demonstrated. Moreover, with more and more urban vehicles being equipped with GPS devices, the designed method can be easily transferred to other cities, thus paving a way for the adoption of the presented approach for an up-to-date and spatial-temporal sensitive road network analysis approach that supports the establishment of a more sustainable urban transport system. [less ▲]

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See detailDetecting urban road network accessibility problems using taxi GPS data
Cui, JianXun; Liu, Feng; Janssens, Davy et al

in Journal of Transport Geography (2016), 51

Urban population growth and economic development have led to the creation of new communities, jobs and services at places where the existing road network might not cover or efficiently handle traffic ... [more ▼]

Urban population growth and economic development have led to the creation of new communities, jobs and services at places where the existing road network might not cover or efficiently handle traffic. This generates isolated pockets of areas which are difficult to reach through the transport system. To address this accessibility problem, we have developed a novel approach to systematically examine the current urban land use and road network conditions as well as to identify poorly connected regions, using GPS data collected from taxis. This method is composed of four major steps. First, city-wide passenger travel demand patterns and travel times are modeled based on GPS trajectories. Upon this model, high density residential regions are then identified, and measures to assess accessibility of each of these places are developed. Next, the regions with the lowest level of accessibility among all the residential areas are detected, and finally the detected regions are further examined and specific transport situations are analyzed. By applying the proposed method to the Chinese city of Harbin, we have identified 20 regions that have the lowest level of accessibility by car among all the identified residential areas. A serious reachability problem to petrol stations has also been discovered, in which drivers from 92.6% of the residential areas have to travel longer than 30 min to refill their cars. Furthermore, the comparison against a baseline model reveals the capacity of the derived measures in accounting for the actual travel routes under divergent traffic conditions. The experimental results demonstrate the potential and effectiveness of the proposed method in detecting car-based accessibility problems, contributing towards the development of urban road networks into a system that has better reachability and more reduced inequity. [less ▲]

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See detailHandling Intra-Household Correlations in Modeling Travel: A Comparison of Hierarchical (Random Effect) Models and Marginal (GEE) Models
Cools, Mario ULiege; Moons, Elke

in Proceedings of the 95th Annual Meeting of the Transportation Research Board (2016)

In this paper, the necessity for treating intra-household correlation is investigated by analyzing two travel behavior indices, i.e. travel time and travel distance, for three important travel motives ... [more ▼]

In this paper, the necessity for treating intra-household correlation is investigated by analyzing two travel behavior indices, i.e. travel time and travel distance, for three important travel motives (commuting, shopping, and leisure). Data stemming from the 2010 Belgian National Household Travel Survey are used in the analysis. Two model approaches that accommodate for intra-household correlation are compared, namely the generalized linear mixed model (GLMM) and GEE model approach. Both model approaches show that high levels of intra-household correlation are present, and therefore the use of models that take into account intra-household correlation, is strongly recommend. Results indicate that this requirement is the most urgent for non-commuting trips. Moreover, the results show that GLMM and GEE yield comparable estimates in the case of normally distributed data. Furthermore, evidence was provided that the more the estimates of the intra-household correlation provided by the two approaches differ, the less the homogeneity of the parameters is assured. In this regard, if one has to choose between the GLMM and GEE methodology, especially the negative consequences of choosing an inappropriate covariance model in the case of a GLMM model favor the selection of the GEE methodology. Further research is needed to compare the two approaches in the context of non-normally distributed travel behavior data. [less ▲]

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See detailAssessing the effect of traveler's nationality on daily travel time expenditure using Zero-Inflated Negative Binomial Regression models: results from the Belgian national household travel survey.
Eftekhar, Hamed ULiege; Creemers, Lieve; Cools, Mario ULiege

in Proceedings of the 95th Annual Meeting of the Transportation Research Board (2016)

In this paper, the effect of traveler's nationality on daily travel time expenditure is assessed using data stemming from the 2010 Belgian national household travel survey. In particular, different (zero ... [more ▼]

In this paper, the effect of traveler's nationality on daily travel time expenditure is assessed using data stemming from the 2010 Belgian national household travel survey. In particular, different (zero-inflated) negative binomial models were estimated to isolate the effect of nationality, after controlling for other contributing factors such as socio-demographics, residential characteristics, transport options and temporal characteristics. The results indicate that, even if one controls for a series of other influencing factors, nationality plays a significant role in differences in travel time expenditure. This finding is especially relevant in the development of policy packages that are targeted to tackle social inequalities. From a methodological perspective, different methodological options, i.e. two weighting schemes and two bootstrap solutions, were presented to provide sufficient support for the conclusions. In order to generalize the results in further studies, an oversampling of travelers with a different nationality is strongly recommended. Future research should focus more on the underlying psychological constructs of why ethnic and cultural differences persist, even if one accounts for other determinants. [less ▲]

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See detailAn integrated framework for forecasting travel behavior using Markov Chain Monte-Carlo simulation and profile Hidden Markov Models
Saadi, Ismaïl ULiege; El Saeid Mustafa, Ahmed Mohamed ULiege; Teller, Jacques ULiege et al

in Proceedings of the 95th Annual Meeting of the Transportation Research Board (2016)

Recent advances in agent-based micro-simulation modelling have further underlined the importance of a thorough full synthetic population procedure to guarantee a correct characterization of the true ... [more ▼]

Recent advances in agent-based micro-simulation modelling have further underlined the importance of a thorough full synthetic population procedure to guarantee a correct characterization of the true population. We propose an integrated approach including Markov Chain Monte Carlo (MCMC) simulation and profiling based methods to catch the complexity and the diversity of agents of the true population through representative micro samples. The population synthesis method is capable of building the joint distribution of a given population with its corresponding marginal distributions (e.g. age, gender, socio-professional status etc.) using complete, partial conditional probabilities or both of them at the same time. Particularly, the estimation of socio-demographic variables and characterization of daily activity-travel patterns are included within the framework. Data stemming from the 2010 Belgian Household Daily Travel Survey (BELDAM) are used to calibrate the modelling framework. We illustrate that this framework catches in an efficient way the behavioral heterogeneity of travelers. Furthermore, we show that the proposed framework is adequately adapted to build large scale micro-simulation scenarios of transportation and urban systems. [less ▲]

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See detailLanduse change and future flood risk: the influence of micro-scale spatial patterns (FloodLand) - 3rd progress report
Dewals, Benjamin ULiege; Bruwier, Martin ULiege; El Saeid Mustafa, Ahmed Mohamed ULiege et al

Report (2015)

The goal of the project FloodLand is to investigate the complex interactions between landuse change and future flood risk. Landuse change is assumed to be mainly driven by population growth and socio ... [more ▼]

The goal of the project FloodLand is to investigate the complex interactions between landuse change and future flood risk. Landuse change is assumed to be mainly driven by population growth and socio-economic factors. It affects future flood risk by altering catchment hydrology as well as vulnerability in the floodplains; but the feedback effect of (the perception of) changes in flood hazard on landuse evolution is also considered. The research is based on a chain of modelling tools, which represent parts of the natural and human systems, including: landuse change modelling, transportation modelling as an onset for the estimation of indirect flood damage, continuous hydrological modelling (forced by precipitation and temperature data disturbed according to climate change scenarios), as well as efficient hydraulic modelling of inundation flow in the floodplains. Besides reproducing a broad spectrum of processes, the modelling approach spans over multiple scales, from the regional or catchment level down to the floodplain and building levels. This distinctive feature is reflected both within the individual models and through their combination involving fine-scale detailed analyses (or data) embedded within coarser models at a broader level. [less ▲]

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See detailModelling Agents’ Behavior in the Context of River Floods: An Ant Colony based Approach
Saadi, Ismaïl ULiege; El Saeid Mustafa, Ahmed Mohamed ULiege; Teller, Jacques ULiege et al

Conference (2015, September)

This paper presents a model for understanding short-term travelers’ behavior in the context of river floods. In several cities, river floods are considerably affecting urban transportation systems. In ... [more ▼]

This paper presents a model for understanding short-term travelers’ behavior in the context of river floods. In several cities, river floods are considerably affecting urban transportation systems. In this regard, decision makers need comprehensive models to define efficient risk management strategies. The dynamic nature of this problem requires an algorithm able to deal with traffic redirecting during the micro-simulation process. Furthermore, a transportation network contains a significant number of links and nodes which lead to large computation times. In this regard, an Ant Colony Optimization (ACO) algorithm is proposed to solve such combinatorial problems. In a basic ACO, some ants/agents might push the algorithm to converge toward non-optimal solutions. In this context, a MAX-MIN Ant System (AS) approach is included in the algorithm to stimulate the best solutions. In addition, the discrete choice model is adapted to allow more behavioral reactions regarding simulated river floods. [less ▲]

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See detailCharacterizing activity sequences using Profile Hidden Markov Models
Liu, Feng; Janssens, Davy; Cui, JianXun et al

in Expert Systems with Applications (2015), 42(13), 57055722

In literature, activity sequences, generated from activity-travel diaries, have been analyzed and classified into clusters based on the composition and ordering of the activities using Sequence Alignment ... [more ▼]

In literature, activity sequences, generated from activity-travel diaries, have been analyzed and classified into clusters based on the composition and ordering of the activities using Sequence Alignment Methods (SAM). However, using these methods, only the frequent activities in each cluster are extracted and qualitatively described; the infrequent activities and their related travel episodes are disregarded. Thus, to quantify the occurrence probabilities of all the daily activities as well as their sequential orders, we develop a novel process to build multiple alignments of the sequences and subsequently derive profile Hidden Markov Models (pHMMs). This process consists of 4 major steps. First, activity sequences are clustered based on a pre-defined scheme. The frequent activities along with their sequential orders are then identified in each cluster, and they are subsequently used as a template to guide the construction of a multiple alignment of the cluster of sequences. Finally, a pHMM is employed to convert the multiple alignment into a position-specific scoring system, representing the probability of each frequent activity at each important position of the alignment as well as the probabilities of both insertion and deletion of infrequent activities. By applying the derived pHMMs to a set of activity-travel diaries collected in Belgium as well as a group of mobile phone call location data recorded in Switzerland, the potential and effectiveness of the models in capturing the sequential features of each cluster and distinguishing them from those of other clusters, are demonstrated. The proposed method can also be utilized to improve activity-based transportation model validation and travel survey designs. Furthermore, it offers a wide application in characterizing a group of any related sequences, particularly sequences varying in length and with a high frequency of short sequences that are typically present in human behavior. [less ▲]

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