The link between travel Time Budget and Speed: a Key relationship for urban space-time dynamics

The relationship between travel time budget (TTB) and speed is central to transport economics and allows us to analyze travel behaviour, urban structure and the transport system. Together, this relationship and Zahavi's hypothesis provide a straightforward mechanism that explains the increase in daily travel distances and urban sprawl. However, quantitative analysis (Regression Analysis and Principal Component Analysis) shows that TTBs are only stable at an aggregate level, and the potential of urban speed restriction policies is severely limited at local level.Travel Time Budget (TTB) ; Travel Behaviour ; Transport Policy ; Urban speed restriction policies

Travel Time Budget – Decomposition of the Worldwide Mean

The paper is concerned with the travel activity and more specifically the urban travel time during a day. This individual mean travel time budget (TTB) has been hypothesised by Zahavi (1980) to be a constant amount of time close to 1 hour per day. This TTB seems to be stable between different cities and between different time periods. Under the TTB stability hypothesis, travel time-savings are totally reinvested in transport. This reinvestment mechanism could then explain the urban sprawl, and give to the increasing speeds all the responsibilities of the “urban transport diseases”. However, the TTB stability seems to be valid at the world aggregate level only. The paper proposes to explore finer scales of observation of the TTB: from the aggregate to the desaggregate levels of observation. First, a worldwide comparison of the mean TTB of 100 cities is produced. Second a hazard based model for the individual TTB of the French city of Lyon is constructed. Hence, two opposite urban models appear at the aggregate level: an extensive urban model of which development is based on extensive consumption of space and time resources, and an intensive urban model restricting its spatial and temporal extension. At the desaggregate level, the analysis identifies the relationships between the individual TTB and the socio-economic variables and the mobility and activities attributes. Finally, the model seems to indicate that the traditional hypothesis of the minimisation of the temporal costs of travel is unsuitable to model the behaviour of the whole urban population.Duration model ; Travel Time Budget ; Zahavi's hypothesis ; Worldwide comparison

The role of travel time budgets – Representation of a demand derived from activity participation

The paper exams the relationships between travel and activity times, in 7 travel surveys from 4 French and 3 Swiss cities, observed at two different periods. First, we test proportional assignment of total daily available time to activities (including transport). Second, proportionality is tested between (1) daily travel time of a given purpose with respect of the daily activity duration and (2) the trip time associated to the duration of the activity at destination. Only daily leisure time and daily travel time are fixed proportion of total daily available time. At disaggregated level, the trip duration do not show proportionality with activity duration. Finally questioning the proportionality and the linear adjustment, we regress the travel time budgets using duration models. This methodology is particularly adapted to the duration analysis and leads to non-linear relation between travel time and activity times. Leisure and shopping activities exhibit increasing and convex travel time intensities.activity-based analysis - time use - travel time

Stability or regularity of the daily travel time in Lyon? Application of a duration model

Escaping unidimensional analysis limits and linear regression irrelevancy, the duration model incorporates impacts of covariates on the duration variable and permits to test the dependence of daily travel times on elapsed time. In the perspective of a discussion of Zahavi's hypothesis, the duration model approach is applied to the daily travel times of Lyon (France). The relationships between daily travel times and socio-economic attributes and activity duration only support the “weak version of TTB stability hypothesis”. Furthermore the non-monotonic estimated hazard questions the minimisation of daily travel times.Duration model; Non-parametric, semi-parametric and parametric approaches; Travel time budget; Zahavi's hypothesis

A duration model for the TTB of Lyon

The paper concerns the travel activities and more specifically the urban travel time during a day. The daily TTB has been hypothesized by Zahavi (1980) as constant amount of time. First, the cities sprawl can easily be interpreted as a consequence of the increase in available speeds. And recently, Schafer and Victor (2000) have used the constant TTB concept to predict the future mobility of the world population. However, numerous critiques exist. The temporal and spatial dimensions of the stability are questioned and the apparent stability observed at aggregate levels may mask considerable variations at finer scale.Escaping unidimensional analysis limits and linear regression irrelevancy, the duration model incorporates impacts of covariates on the duration variable and permits to test the dependence of TTB on elapsed time. We apply the duration model to the TTB of Lyons (France), in the perspective of a discussion of Zahavi's hypothesis. The duration dependence estimation illustrates covariates effect on TTB and suggests a non-monotone hazard for their distribution, which conflicts with the TTB stability hypothesis and more generally with the classic travel time minimisation problem.TTB ; Zahavi's hypothesis ; duration model ; non-parametric / semi-parametric / parametric approaches

Préserver la constance du budget temps de transport : Le réinvestissement des gains de temps

Le rapport revient, dans sa première partie, sur la définition de l'hypothèse de Zahavi, telle qu'il l'a définie. Cette définition est ensuite confrontée à la "loi de Zahavi", c'est à dire à l'idée reçue de l'hypothèse de Zahavi. Dans un second temps, le rapport analyse, le réinvestissement des gains de temps au moyen d'une représentation microéconomique. Puis ses conséquences sur la mobilité et son impact sur la structure urbaine sont présentés.Budgets-temps de transport ; allocation du temps ; comportement de mobilité

WHEN CELEBRITY DESTROYS ARTISTIC REPUTATION: THE CASE OF FRENCH ARCHITECTS

This paper suggests understanding better the debate between reputation and celebrity, by analyzing how various types of reputations can combine (or not) to achieve celebrity. Based on a quantitative analysis of the most reputed French architects, we contribute to the reputation and celebrity literatures.Reputation; Celebrity; Stakeholders; Creative sector; Architecture

L'hypothèse de Zahavi revisitée. Quelle pertinence ?

L'article s'appuie sur la base de l'UITP, « The millenium Cities Database » afin d'explorer les rapports espace-temps de la mobilité des villes du monde. L'étude des budgets temps de transport qu'il présente teste la validité de l'hypothèse de Zahavi. En renseignant les trois aspects de la mobilité (comportement, système d'offre et structure de l'espace) la base de l'UITP permet de dresser une « image arrêtée » des systèmes de mobilité du monde pour l'année 1995, et de définir des profils types d'organisation urbaine. Un développement par densification de la ville s'oppose à un développement par extension de la ville. L'observation des consommations des ressources espace-temps des villes fait apparaître que contrairement au modèle extensif, le modèle dense retient ses consommations temporelles et spatiales. Par la croissance de ses consommations d'espace, mais surtout de temps, le modèle extensif remet en cause l'hypothèse de Zahavi. Cette analyse permet alors de critiquer l'un des fondements des mécanismes de l'étalement urbain, et de remettre en question le lien de causalité décrit jusqu'à présent entre les gains de vitesses et la croissance des distances parcourues : le réinvestissement total des gains de temps en transport.Budgets temps de transport ; hypothèse de Zahavi ; base de données (UITP) ; Organisation du système de transport

The determinants of urban public transport: an international comparison and econometric analysis

The analysis presented in this paper is based on the database created by the UITP (International Association of Public Transport), "The Millennium Cities Database", which covers the public transport systems in 100 of the world's cities. It contains data on demography, urban structure, transport networks, daily mobility, environmental impacts, etc. Our analysis demonstrates the contrasts between European and American travel practices. It explores possible links between public transport market share and geographical and economic conditions on the one hand and the characteristics and performances of public transport systems on the other. Our research has generated an explanatory econometric model for public transport market share. To end with, a consideration of the levers that can be used to influence the public transport system leads into a discussion about the future of cities with ''European urban mobility'' and the danger of a slide towards ''American urban mobility'' taking place.Transport systems ; Urban mobility ; Transport policy ; Public transport

A shared frailty semi-parametric markov renewal model for travel and activity time-use pattern analysis

This study investigates the influence of observed explanatory factors and unobserved random effect (heterogeneity) on episode durations of travel-activity chain. A shared frailty semiparametric proportional hazard model is proposed to estimate the transition hazard of travel/activity states. The proposed model is applied on the travel and activity episode duration analysis during evening work-to-home commute using the household travel survey data collected in the city of Lyon in France in 2005-2006. The empirical results provide useful insights for the determinants of travel and activity episode durations for evening work-to-home commute.time-use; activity duration; Markov renewal model; shared frailty; heterogeneity