Eurocities Datta

Recent studies on space consumption and travel time budgets reveal a deviation towards an expansion of space and time use by residents in European urban areas. This phenomenon refers directly to sustainability issues, since "intensive" European cities pattern could conceivably derive towards extensive models, like North American cities, that gradually experience a lack of resources, such as fossil energy with its consequences on climate change, and over-utilisation of space and even time for travel.

The primary objective of this research proposal is to explore the factors that influence distances travelled and travel duration. Special attention will be given to their implications on spatial, temporal, and social dimensions of activity patterns. Travel time appears to be a suitable and pertinent perspective to study the interrelations between the spatial, temporal and social dimensions of mobility and activity behaviour.

In this framework, the time-geography paradigm formulated by Hägerstrand is vital. This approach represents mobility behaviour as an integrated part of a continuous path through space and time, i.e. an activity pattern. This is a way to firstly introduce the space-time constraints on activity pattern, resulting basically from the limitations of transport speed This progressively evolves from a travel perspective to an activity one, which also considers that the individual performing the activity is influenced by a social context (e.g. familial or professional relationships). This social element leads to interpersonal constraints between individuals or social groups. Geographers and urban planners have since used this approach to analyse activity patterns, simultaneously referring to both their temporal and geographic dimensions. Sociologists and economists equally have incorporated these aspects in their research about mobility behaviour. Traditionally, for transportation economists, the mobility behaviour of individuals can be analysed as a trade-off between the utility of an activity at destination (the wage earned by working, the benefits of going shopping, seeing a movie, etc) and the disutility, or the cost of the trip, including its monetary cost and the accepted time devoted to travel. However, this perspective has been greatly modified with the influence of time-geography. Travel is therefore viewed as a demand derived from the need to participate in activities that are dispersed in space and time. Within this new framework of an activity-based approach, transportation is nothing more than one of the many attributes of an activity. The understanding of mobility behaviour consequently becomes secondary to the fundamental understanding of activity behaviour.

Numerous methodologies have been implemented on activity duration, the order of activities performed, or the specific scheduling of activities. Studies on the seasonality of activity and mobility (weekly or monthly rhythms) indicates the existence of cycles on different temporal levels. Nevertheless, few studies on travel
and activity times explicitly integrate spatial elements. In the past, this spatial aspect has been considered by an accessibility indicator, such as the one proposed by Hanson that refers to the trade-off between the utility of the opportunities at a
destination (e.g. employment) and the disutility of travel (as described previously). For example, the gravity spatial interaction model that distributes trips between origin and destination zones refers to this indicator. However, this gravity indicator again only concerns trips separately. The activity-based approach no longer considers the elementary choices of a trip, but rather all the choices undertaken within an activity pattern. This kind of model permitted the development of an Activity Based Accessibility indicator (ABA). Another approach combines the space-timeapproach developed by geographers and the theory of discrete choice by economists to create Space Time Accessibility Measures.

Sociologic approaches on travel times have enlightened the great complexity of mobility / temporality relationships. These studies focus on the individual reasons, intentional or unconscious, to devote more or less amounts of time to travel.

Although the current developments integrate correctly the effects of distance and transportation speed through the monetary cost of mobility and the time necessary to arrive at a destination, they also have difficulties to integrate the complexity of the allocation of available time during the day, using both individual and social interaction dimensions.

Therefore, the objective of Eurocities Datta is to renew this complex issue of activity pattern analysis by undertaking an innovative approach: the analysis of travel duration and its relationship with the duration of activities at a destination. We expect this will provide us with a sound approach to question the makeup of activity patterns within an urban space characterised by heterogeneous spatial
accessibilities.

The study of these various dimensions, including their interrelations with mobility behaviours, cannot be conducted within a unique disciplinary view. The interdisciplinary character of the subject is the reason of our partnership, incorporating diverse methods and viewpoints. To analyse and unify the numerous
dimensions of the activity-based and time-geography approach, we have adopted an interdisciplinary methodology. The three partners (LET, LaSUR and GRT) research themes range from economics, to econometrics, statistics, sociology, and geomatics. In addition to the interdisciplinary character of the partnership, the three teams are also willing to progressively build an European-wide project. In this perspective, the project intends to motivate other international research teams that could contribute to the knowledge of urban mobility from different European countries, and to offer methodological views adapted to interdisciplinary discussions. Organisation of half-yearly international seminars will create appropriate opportunities topresent and discuss the themes concerned in the project.