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Working Paper
Moving through netsAn introduction
Author(s): Axhausen, Kay W.
Publication Date: 2006-02
Permanent Link: https://doi.org/10.3929/ethz-a-005226264
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Introduction
Moving through nets: An introduction
K.W. Axhausen
Arbeitsbericht Verkehrs- und Raumplanung 348 February 2006
Introduction ..._______________________________________________________________________ February 2006
1
Arbeitsbericht Verkehrs- und Raumplanung
Sich in Netzen bewegen: Eine Einleitung
K.W. Axhausen
IVT
ETH
CH – 8093 Zürich
Telefon: +41-1-633 3943
Telefax: +41-1-633 1057
February 2006
Kurzfassung
Dies ist die Einleitung des Buches zur 10th International Conference on Travel Behaviour Research, die im August 2003 vom IVT in Luzern organisiert wurde.. Es skizziert einen theoretischen Rahmen für die in der Konferenz präsentierten Arbeiten.
Schlagworte
10th International Conference on Travel Behaviour Research, Luzern, IATBR
Zitierungsvorschlag
K.W. Axhausen (2005) Moving through nets: An introduction, in K.W. Axhausen (ed.) Moving
Through Nets: The Physical and Social Dimensions of Travel, xx-xx, Elsevier, Oxford.
Introduction ..._______________________________________________________________________ February 2006
2
Working paper
Moving through nets: An Introduction
K.W. Axhausen
IVT
ETH
CH – 8093 Zürich
Telephone: +41-1-633 3943
Telefax: +41-1-633 1057
February 2006
Abstract
This introductory chapter sketches a conceptual framework for the papers presented at the 10th International Conference on Travel Behaviour research, which was organised by the IVT in Lucerne during August 2003..
Keywords
10th International Conference on Travel Behaviour Research, Lucerne, IATBR
Preferred citation style
K.W. Axhausen (2005) Moving through nets: An introduction, in K.W. Axhausen (ed.) Moving Through Nets: The Physical and Social Dimensions of Travel, xx-xx, Elsevier, Oxford.
Introduction ..._______________________________________________________________________ February 2006
3
1 A reframing
Travel behaviour research, in particular that informed by the activity-based viewpoint, has
expanded our understanding of travellers and their choices enormously. The International
Association of Travel Behaviour Research (IATBR) has furthered this process through its
now long-standing series of tri-annual conferences (see Table 1 below). Their proceedings
and the literature generally document the increasing refinement of our conceptual frameworks
and models for the behaviours and choices of travellers on individual days. Taste differences,
lifestyles, attitudes and sociodemographics have been added to the description of choice
situations, which are driven by the relative, generalized costs of the activities and their
associated travel. What is mostly missing in the current analysis is a framing, which would
integrate the short- and long-term dynamics of travellers. While the industrialized world will
never again see a similarly dramatic shrinking of its time-space system as it did during the last
fifty years (see Figure 1 for the Swiss example), other major changes should force travel
behaviour analysis to adopt fully dynamic frameworks.
Figure 1 Road travel time-scaled mapping of Switzerland (same scale)
1950 2000
Source: Axhausen and Hurni (2005)
The changes and challenges to the field are both external and internal. The recent difficulties
and costs involved in expanding infrastructure capacity have led to increasing reliance on
demand management approaches to balance the loads on the networks. Transport telematics,
Action spaces, biographies, social networks.. ______________________________________________ February 2006
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on-line traffic control, road pricing, revenue management of the airlines, but also employer-
based “green travel” come to mind. All of these work because travellers have some flexibility
with regard to their timings, above and beyond other possible changes to their schedule such
as route, mode or destination. These changed timings are likely to affect other days than just
the current one and therefore suggest models which are able to address sequences of days.
The internal logic of the past thirty years of model development points to the microsimulation
of all travel in a study area as the appropriate approach for transferring the results of activity-
based travel analysis into practise. Microsimulations are inherently dynamic and are therefore
able to welcome the external emphasis on behaviour interactions over time. Additionally, the
limitations of the current set of variables to explain behaviour have become clear. While the
models often have good fits, there remains an unease, especially about trip generation, the
stability of behaviour over time, the joint choices of groups and households, the formation of
choice sets and finally the selection and formation of choice rules by travellers. From the
dynamic perspective, and also against an analysis of the missing variables, two issues (and
variable groups) seem obvious: the information assembled by travellers via their biographies,
and the information and abilities inherent in their social networks.
Figure 2 The individual in a dynamic social context
Personalworld
Biography
Projects Learning
Personalworlds of
others
Sharedhistory
and commitments
Household locationsSocial network geography
Mobility tools
Personalworld
Personalworld
Biography
Projects Learning
Personalworlds of
others
Sharedhistory
and commitments
Household locationsSocial network geography
Mobility tools
Action spaces, biographies, social networks.. ______________________________________________ February 2006
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Figure 2 above tries to summarize this view of the traveller in a dynamic social context. The
personal world of the traveller is perhaps better known as his or her mental map, but that
image is limiting, as it emphasizes the geography of the activity space at the expense of other
important elements of knowledge: types of activities known, when and with whom to
undertake them, and the opening hours of facilities. An alternative term for this knowledge
would be activity repertoire, which in turn is weak because it does not refer to the geography
of activity participation. Drawing on the knowledge accumulated over the course of a lifetime,
the traveller selects projects against the background of his or her current commitments.
Longer-term household locations (including workplaces, regularly used shops and other
facilities), social networks and the available mobility tools (such as licences, motorized
vehicles, public transport season tickets and bicycles) are mentioned in Figure 2 The members
of the social network and their personal worlds are both resources and constraints. Their
knowledge, their abilities and their material resources can be drawn on within the limits of
convention and the strength of the personal relationship, which gives the individual extra
leverage in his or her daily life. Their locations, abilities and resources are also limiting, as
they have to be considered in decision making. Consider the trivial case of the joint choice of
a restaurant if one of the members of the group has particularly strong dislikes, such as an
aversion to a cuisine, or is allergic to, say, seafood.
Such a dynamic view of the individual requires a division of the modelled processes into
short-term and long(er)-term ones. One possibility for such a division is suggested in Figure 3
and Figure 4. The understanding sketched here does not require an equilibrium concept, but
assumes a willingness on the part of the individual to improve his or her situation
incrementally. While behaviourally appealing, such an approach might still need equilibrating
mechanisms to produce consistent results in application timeframes.
The central process for the short term (Figure 3) is the formulation of schedules, such as the
complete description of a day (number, type and sequence of activities, their durations and
locations, modes and routes, finally group size and composition for travel and activities). It is
assumed here that the scheduler draws from an activity calendar which lists the activities or,
more generally, activity types that the traveller has to accomplish due to project engagements,
commitments, physiological needs or desires. This list reflects the activity repertoire of the
person, which can be expanded through interaction with others and the environment. As
people generally aim to improve and possibly even optimize their schedules, they will draw
on their mental maps to reduce the effort and uncertainties of the day. We know that
travellers, as a rule, do not fully book their days, but leave slots for the unexpected and the
unplanned. In a simulation framework it might be necessary for the sake of computational
Action spaces, biographies, social networks.. ______________________________________________ February 2006
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convenience to impose the assumption that the current day has been fully allocated by some
arbitrary point of time in the previous night.
Figure 3 Modelling the individual’s day-to-day dynamics
The execution of the schedule requires interacting with others in the networks and in activity
opportunity places such as shops, cinemas or other persons’ homes. In some cases the
resulting congestion or the failure of an activity opportunity to deliver the expected service or
good forces travellers to adjust and to reschedule. At the end of the day, travellers will have
updated their knowledge about the elements in their activity repertoires and mental maps.
They may have developed new solutions to the fulfilment of their needs by trying new routes,
modes or locations, by drawing on new information, by expanding their expectation space or
by accepting solutions proposed by others on the basis of their knowledge. The expectation
space is a third view of the personal world. It is the set of heuristics which people develop
about the environment, and their generalizations about the organization of space. Examples
are the heuristics of how and where to find a gasoline station in an otherwise unknown part of
town or expectations about the store composition of a local shopping mall.
Longer-term processes, which structure the shorter-term ones, revolve around the projects
which a traveller formulates to translate his or her life goals and his or her understanding of
him- or herself into reality. In any one period these projects need to be sequenced to provide a
Activity repertoire (t) Activity repertoire (t+1) ................
Activitycalendar (t)
Physiological needsCommitmentsDesiresPending activities
Activityschedule (t)
Mental map (t) Mental map (t+1) ................
Scheduling
Networks, Opportunities
Rescheduling,Execution
Updates,Innovations
Unexecutedactivities
Activity repertoire (t) Activity repertoire (t+1) ................
Activitycalendar (t)
Physiological needsCommitmentsDesiresPending activities
Activityschedule (t)
Mental map (t) Mental map (t+1) ................
Scheduling
Networks, Opportunities
Rescheduling,Execution
Updates,Innovations
Unexecutedactivities
Action spaces, biographies, social networks.. ______________________________________________ February 2006
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reasonable load and prioritization. This planning requires negotiation with others, as many
projects will depend on synchronization with, input of, presence of or permission of others.
Again, the interaction with still others in the markets and networks during execution will
require adjustments and changes, including the abandonment of certain projects or project
elements. The experience will update and expand the individual’s personal world, but also
shape the set of life goals pursued in the next time interval.
Figure 4 Modelling the individual’s longer-term dynamics
The impact on travel behaviour modelling of such a reframing of the task would be profound.
It would move the centre of attention away from the idea of equilibrium and towards concepts
such as innovation, solution generation, life goals and commitments to people and ideas.
These concepts are not unknown to activity-based travel behaviour analysis, but they would
need to be moved centre-stage.
(Life) goals (t) (Life) goals (t+1) ................
Projects (t)[committments]
Definition of „Self“DesiresPending projects
Projectsequence (t)
Personal world (t) Personal world (t+1) ................
Planning, Negotiation
Markets and networks
Replanning,Execution
Updates,Innovations,Reflection
Unexecutedprojects
(Life) goals (t) (Life) goals (t+1) ................
Projects (t)[committments]
Definition of „Self“DesiresPending projects
Projectsequence (t)
Personal world (t) Personal world (t+1) ................
Planning, Negotiation
Markets and networks
Replanning,Execution
Updates,Innovations,Reflection
Unexecutedprojects
Action spaces, biographies, social networks.. ______________________________________________ February 2006
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2 Acknowledgements
This book documents the reviewed keynote papers of the 10th International Conference on
Travel Behaviour Research in Lucerne, August 2003. It gives an excellent, state-of-the-art
overview of the key concerns of the travel behaviour research community. The authors of the
papers were free to achieve this goal by presenting reviews or by challenging through a focus
on new and innovative aspects of the area. The titles of the papers and the names of the
authors speak for themselves, so I will forgo the usual capsule summaries of a book
introduction.
Such an event and the associated book is the product of many hands, which I have the
pleasure and duty to acknowledge.
Dr. Robert Schlich was the main local organizer who made sure that the event during the
hottest week in living memory worked smoothly in an only partially air-conditioned building.
The building, which was ideally suited for our purposes, had generously been made available
by the Schweizerische Hotelfachschule of Lucerne. Dr. Robert Schlich was able to draw on
his colleagues at the Institute for Transport Planning and Systems, ETH Zürich, who set up
the projectors, fixed lap top problems and undertook all the further less exciting but necessary
tasks of such a conference (Sigrun Beige, Saikumar Chalasani, Phillip Fröhlich, Jeremy
Hackney, Arnd König, Stefan Sandmeier, Stefan Schönfelder, Martin Tschopp and Milenko
Vrtic).
The local organizing committee provided important and generous input during the three-year
preparation of the conference: Dr. Michel Bierlaire, EPF Lausanne; Prof. Rico Maggi, USI,
Lugano and Prof. Kai Nagel, then ETH Zürich. The committee was again supported by Dr.
Robert Schlich during this phase. In the same spirit, we were able to draw on the advice and
help of the members of the scientific committee of the conference and of the members of the
IATBR board, who unfortunately are too numerous to list here.
An international conference needs financial support, which was kindly provided by the
Schweizer Nationalfonds, Bundesamt für Strassen, Bundesamt für Raumentwicklung, ETH
Zürich, EPF Lausanne, Universita de la Svizzera Italiana, Migros Kulturprozent, Swiss
Federal Railroads, the Urban Transport Institute and educatis.ch.
The production of this book benefited from the careful and intensive copyediting of Judith
Diane Weston, Karlsruhe, and from the graphic design skills of Andreas Gähwiler, ETH
Zürich.
Action spaces, biographies, social networks.. ______________________________________________ February 2006
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3 Literature
Axhausen, K.W. and L. Hurni (eds.) (2005) Zeitkarten Schweiz 1950-2000, IVT and IKA, ETH Zürich, Zürich.
1 History of the series
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Table 1 History of the series
Year Location Title Reference
1 June 1973 South Berwick, Maine
Issues in Behavioral Demand Modeling and the Evaluation of Travel Time
TRB (ed.) (1974) Behavioral Demand Modeling and Valuation of Travel Time, Special Report, 149, Transportation Research Board, Washington, D.C.
2 May 1975 Asheville, North Carolina
Second International Conference on Behavioral Travel Demand
Stopher, P.R. and A.H. Meyburg (eds.) (1976) Behavioral Travel-Demand Models, Lexington Books, Lexington.
3 April 1977 Tanunda, South Australia
Third International Conference on Behavioural Travel Modelling
Hensher, D. A. and P.R. Stopher (eds.) (1979) Behavioural Travel Modelling, Croom Helm, London.
4 July 1979 Grainau, Germany
Fourth International Conference on Behavioural Travel Modelling
Stopher, P.R., A.H. Meyburg and W. Brög (eds.) (1981) New Horizons in Travel-Behavior Research, Lexington Books, Lexington.
5 October 1982
Easton, Maryland
Fifth International Conference on Travel Analysis Methods
TRB (ed.) (1983) Travel analysis methods for the 1980s, Special Report, 201, Transportation Research Board, Washington, D.C.
6 April 1985 Nordwijk, Netherlands
1985 International Conference on Travel Behaviour
Rijkswaterstaat (ed.) (1986) Behavioural Research for Transport Policy, VNU Science Press, Utrecht
7 October 1987
Aix-en-Provence, France
Fifth International Conference on Travel Behaviour
International Association for Travel Behaviour (ed.) (1989) Travel Behaviour Research, Avebury, Aldershot.
8 May 1991 Quebec, Quebec International Conference on Travel Behavior Research
Stopher, P.R. and M.E.H. Lee-Gosselin (eds.) (1997) Understanding Travel Behavior in an Era of Change, Pergamon, Oxford.
9 June 1994 Valle Nevada, Chile
Seventh International Conference on Travel Behaviour
Ortuzar, J. de Dios, D.A. Hensher and S. Jara-Diaz (eds.) (1998) Travel Behaviour Research: An Update, Pergamon, Oxford.
10 September 1997
Austin, Texas Eight International Conference on Travel Behavior Research
Mahmassani, H. (ed.) (2002) In Perpetual Motion: Travel Behaviour Research Opportunities and Application Challenges, Pergamon, Oxford.
11 June 2000 Goldcoast, Queensland
Ninth International Conference on Travel Behaviour Research
Hensher, D.A. (ed.) (2001) The Leading Edge in Travel Behaviour Research, Pergamon, Oxford.
12 August 2003
Lucerne, Switzerland
Tenth International Conference on Travel Behaviour Research
Axhausen, K.W. (ed.) (2005) Moving Through Nets: The Physical and Social Dimensions of Travel, Pergamon, Oxford.
13 August 2006
Kyoto, Japan Eleventh International Conference on Travel Behaviour Research
The Expanding Sphere of Travel Behaviour Research
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