Surveying activity-travel behavior in Flanders: Assessing the impact of the survey design

peer reviewedEver since car ownership and car use started to increase in Western Europe and the USA, transportation planners attempted to model people’s travel behavior. In the context of the Feathers project a dynamic activity-based travel demand framework is developed for Flanders. In this paper, the complete survey design of the data collection effort required for such dynamic activity-based model is discussed. A mixed survey design of using a PDA application on the one hand, and using traditional paper and pencil diaries on the other hand, turns out to be a very suitable way of collecting detailed information about planned and executed activity-travel behavior of households. The results show that no attrition effects are present, not on the number of out-of-home activities reported, nor on the number of trips reported. Moreover the survey mode (PDA versus paper and pencil) has no direct impact on the quantities investigated. Notwithstanding, it is essential for further analysis on the Feathers data to explicitly take into account mode effects because of two reasons. First, the effect of explanatory variables can be influenced by the survey mode. Second, the variance in the estimation of the quantity investigated can differ significantly. Heteroscedatisc linear regression models provide the required framework to explicitly take into account these mode effects

Adapting a Local Indicator of Spatial Association to Identify Hot Spots in Traffic Safety

Abstract In the last years, traffic safety has become a 'hot' topic in the media, for policy makers, for academics and for the broad audience. In general, traffic safety analysis can be split up in four phases: identification of hot spots, ordering, profiling of the hazardous locations and finally selecting the locations that need to be handled. This paper will focus on phase 1. Several spatial measures have been developed to identify hot spots, however, not all measures are equally well suited in the field of traffic safety. E.g. a high-accident location is always of interest for hot spot analysis, but a low-accident location may be of interest if its neighbouring locations show an opposite behaviour regarding the number of accidents. In this paper we will present an adaptation of a local measure of spatial association, more in specific of Moran's I and apply it to identify hot spots on highways

Fertility, pregnancy and delivery in women after biventricular repair for double outlet right ventricle

Objectives: To investigate outcome of pregnancy and fertility in women with double outlet right ventricle (DORV). Methods: Using 2 congenital heart disease registries, 21 female patients with DORV (aged 18-39 years) were retrospectively identified. Detailed recordings of each patient and their completed (>20 weeks gestation) pregnancies were recorded. Results: Overall, 10 patients had 19 pregnancies, including 3 spontaneous miscarriages (16%). During the 16 live birth pregnancies, primarily (serious) noncardiac complications were observed, e.g. premature labor/delivery (n = 7 and n = 3, respectively), small for gestational age (n = 4), preeclampsia (n = 2) and recurrence of congenital heart disease (n = 2). Except for postpartum endocarditis and deterioration of subpulmonary obstruction, only mild cardiac complication pregnancies were recorded. Two women with children reported secondary female infertility. Several menstrual cycle disorders were reported: secondary amenorrhea (n = 4), primary amenorrhea (n = 3) and oligomenorrhea (n = 2). Conclusion: Successful pregnancy in women with DORV is possible. Primarily noncardiac complications were observed and only few (minor) cardiac complications. Infertility and menstrual cycle disorders appear to be more prevalent. Copyrigh

Psychosocial impact of implantable cardioverter defibrillators (ICD) in young adults with Tetralogy of Fallot

Item does not contain fulltextOBJECTIVE: To investigate the psychosocial impact of having an implantable cardioverter defibrillator (ICD) in adults with Tetralogy of Fallot (ToF). METHODS: Included were 26 ToF-patients with an ICD (age 44 +/- 12 years), and two control groups consisting of 28 ToF-patients without an ICD (age 40 +/- 10 years) and a group of 35 ICD-patients of older age without ToF (age 72.0 +/- 8 years). This last control group was chosen to represent the "older general ICD population" with acquired heart disease seen at the out-patient clinic. Psychosocial functioning encompassed daily functioning, subjective health status, quality of life, anxiety, depression, coping and social support. RESULTS: ToF-patients with ICD showed diminished psychosocial functioning in comparison to ToF-patients without ICD. This was reflected by diminished subjectively perceived physical functioning (p = 0.01), general health perception (p < 0.01) and a lower satisfaction with life (p = 0.02). In comparison to older ICD-patients, ToF-patients with ICD showed less satisfaction with life (p = 0.03), experienced more anxiety (p = 0.01) and showed less favourable coping styles, although physical functioning was better for ToF-patients with ICD than for older ICD-patients (p = 0.01). More inappropriate shocks were found in ToF-patients with ICD compared to the older ICD-patients. CONCLUSION: In patients with ToF, ICD implantation had a major impact on psychosocial functioning which should be taken into account when considering ICD implantation in these young patients. To help improve psychosocial functioning, psychological counselling attuned to the specific needs of these patients may be useful.1 juli 201

Handling Intra-Household Correlations in Modeling Travel: A Comparison of Hierarchical (Random Effect) Models and Marginal (GEE) Models

peer reviewedIn 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.VEEA

Travel time expenditure in Flanders: Towards a better understanding of travel behavior

peer reviewedIn modern societies, mobility is considered to be vital for human development. In order to lead an efficient policy and achieve environmental goals, governments require reliable predictions of travel behavior. In this paper, the travel time expenditure in Flanders is investigated. The focus is put on the time spent on commuting. Two modeling approaches are used for the analysis of daily travel time expenditure, namely the Poisson regression approach and the classical linear regression approach. In this paper it is shown that socio-demographics, day-effects and transportation preferences are contributing significantly in the explanation of variability in daily commuting time and that multiplicative effects of the transportation preferences form good approximations of the travel time ratios

The use of time use surveys to study activity participation: emerging issues

Time use surveys often are carried out to identify, classify and quantify social behaviour of people by focusing on the activities that people perform. Time use data, in the transportation field often referred to as activity-based data, can be used to study a variety of sociological, economic, and technological phenomena. Studying behaviour, social networks and transport patterns are a few of the topics that can be analysed based on these time use data. This first introductory paper discusses some emerging issues in the collection of travel-related data such as automatic spatial information recording using cell phones and GPS, and survey design experiences. On the one hand new technology offers the opportunity to record at a relative low cost a wide variety of the data, while on the other hand new problems occur. One of such problems for instance is the problems of ‘cold starts’ faced with GPS devices, clouding the first minutes of recording after each restart of the device after it was turned off completely. Notwithstanding, applications of new technologies offer the opportunity for performing detailed space-time analyses in different fields ranging from epidemiology to transportation science. Some of these applications are highlighted in this session. Next to the advantages and potential risks of new technologies, this introductory paper also discusses the combination of different modes to analyze space-time behaviour. In particular, this study investigates potential mixed mode design effects, observed in a large activity-based travel survey, using a PDA application on the one hand, and traditional paper and pencil diaries on the other hand. The mixed-mode effects are analysed using heteroscedastic linear regression models, taking into account not only mode-effects, but also potential fatigue-effects. The results show that in this mixed-mode survey no attrition effects are present, and that the survey mode (PDA versus paper and pencil) has no direct impact on the quantities investigated (number of out-of-home activities reported and number of trips)

Regular events in travel behaviour research: setup of a longitudinal websurvey

One of the leading paradigms in modern travel behaviour research is the activity based approach, which considers travel as a derivative from the activities that individuals and households need or wish to perform. Longitudinal designs provide the required framework for a better understanding of the dynamics of travel behaviour. Longitudinal data can be used to analyze behavioural adjustments some time before (response leads) or after (response lags) the occurrence of an event, or for instance to analyze routine behaviour. The questionnaire used to collect the data will be an activity diary. The respondents are asked to fill in all their activities performed that day. The diaries have to be filled in at least twice a week. These moments are randomly selected, but in weeks when a special event occurs, the days around this special event are questioned as well. Performing a longitudinal study has certain drawbacks however. The respondent burden can cause different side-effects, such as panel attrition, decreasing representativeness and, reporting errors. Thus, next to refreshing the sample regularly, trying to keep the respondents motivated is essential. A first step in lowering the respondent burden is to make the activity diaries user-friendly. An internetbased questionnaire makes interaction with respondents possible. The respondent’s current results can be graphically displayed (e.g. geographical map of activity-pattern), potentially awakening or strengthening the interest in the study. Logical rules (e.g. two activities on two different locations require a trip in between) can be formulated, and the interaction with the respondents allows the researcher to get feedback on “strange” answers, or on missing values, thus improving the data quality. This paper describes some potential paths to minimise sample attrition (e.g. internet-based interaction with respondents) and ways to refresh the sample. These findings are applied to the study of travel behaviour of Flemish households around school holidays

Modeling Daily Traffic Counts: Analyzing the Effects of Holidays

peer reviewe