Penguins and travel time budgets

wiki stan shebsResearchers Shinichi Watanabe, Katsufumi Sato, Paul J. Ponganis recently published an article (see here) on “Activity Time Budget during Foraging Trips of Emperor Penguins.” Other articles have  been published on the daily time budgets of different animals (see for example here). The question then is, if animals have time budgets, do humans have them as well?

In transportation studies there is a theory of constant travel time budgets; but there are also articles which both support it and which are against it. 

What it is

Travel time budgets is a concept that says people spend a fixed amount of hours per day in travel. As the useful document on accessibility from the Victoria Transport Policy Institute (VTPI) says:

People throughout the world tend to spend about the same amount of time on travel, averaging about 1.2 hours per day (Schafer, 2000). After all, there are only so many hours in a day, part of which is devoted to sleep, work and other personal activities. As a result, people tend to adapt their lives to their accessibility. For example, when a person first obtains a bicycle or automobile, they don’t usually simply travel faster to the same destinations, they usually spend about the same amount of time traveling to more distant destinations. Conversely, if your accessibility improves, for example, if several stores open near your home, you may visit them more frequently than if shopping trips require several miles of travel. As a result, travel time budgets tend to remain constant as mobility and land use accessibility change.

The concept is expressed by Marchetti’s constant. The Wikipedia page on this says “Even since Neolithic times, people have kept the time at which they travel per day the same, even though the distance may increase”. The same Wikipedia page refers to the work of Yakov Zahavi, who “also noticed that “people seem to have a constant ‘travel time budget’.

Other articles in favour of the concept of Travel Time Budgets

Thomas Longden (ref. 724 / 2012) says that Schafer and Victor (2000) noted that time use surveys and travel surveys tend to show travel budgets are approximately 1.1 hrs per person per day.

David Metz (ref. 725/ 2008) says “…. in  the  long  run average travel time is conserved, implying that travellers take the benefit of improvements in the form of additional access  to more distant destinations made possible by higher speeds”.

Arnulf Grübler (ref. 325 / 1990) in a very detailed work, says “Empirical evidence suggests that the time devoted by an individual (on average) to transportation appears to be close to an anthropological constant: it ranges from around 1 to 1.5 hours per day, both in rural-agricultural and in urban-industrial societies.”

Articles against the concept of Travel Time Budgets

Frank Milthorpe (ref. 723 / 2007) concludes

Analysis of  the Sydney travel surveys have shown that there has been an increase in the average daily travel times in the period 1981 to 2005. This result is consistent with findings from North America and some European countries and in contrast to the findings in Great Britain.


Whilst the analysis and reporting of mean travel time is a convenient measure (….) it  masks  the  considerable  variation between individuals. We also suspect that there is considerable variation in the travel times of an individual on a day to day basis (and)  from  the  analysis  undertaken  there  is  variation  in  the  daily travel  times  between  genders  and age-groups.

Van Wee et al (ref.722 / 2002) say that “recent research suggests that during the past decades the average travel time of the Dutch population has increased”.

Mokhtarian and Chen (ref. 706 / 2003) conclude that

At the aggregate level, travel expenditures initially appear to have some stability (but also) At  the  disaggregate  level,  there  is  a  high  degree  of  variation  in  both  travel  time  and  money expenditures (Kirby, 1981).  Even proponents of a constant travel time budget acknowledge this variation, which appears in aggregate studies as well.  For example, Zahavi and Talvitie (1980, p.  18),  after  asserting  “the  inescapable  conclusion  that  travel  time  and  money  budgets  exist”, express the “belief that travel time and money budgets are not constant, but they are functions of several variables”

So that:

The  overall  conclusion  we  draw  from  these  studies,  then,  is  that  the  claim  of  the  definitive existence  of  constant  travel  time  and  money  budgets  in  time  and  space  is  not  supported.


Maybe transportation studies researchers should team up with zoologists and other experts on animal behaviour to establish a basic concept of human behaviour patterns. At the moment my own feeling is still that there is substance to the idea of travel time budgets – which is one reason why I suspect that cost benefits from travel time savings are not real.

On this point the recent IBRD / World Bank publication by Robert Cervero (ref. 730 / 2011) is worth reading. For example the abstract includes this text:

“This paper challenges the widespread and often indiscriminant use of travel-time savings as a principal metric of economic benefits for evaluating urban transport projects. Time-budget theory and empirical evidence reveals that the benefits of a widened road or extended rail line often get expressed by more and longer trips to larger numbers of destinations and not by less time spent traveling”.


The photograph is from wikipedia / Stan Shebs (link)

325 – Grübler, Arnold “The rise and fall of infrastructures”, Physica-Verlag Heidelberg, 1990

706 – Mokhtarian and Chen, “TTB or Not TTB, that is the Question: A Review and Analysis of the Empirical Literature onTravel Time (and Money) Budgets” Paper submitted to Transportation Research, USA 2003

722 – Van Wee, Rietveld, Meurs, “A constant travel time budget? In search for explanation for an increase in average speed”, University of Amsterdam 2002

723 – Milthorpe, Frank , “Consistency in Daily Travel Time – An Empirical Assessment from Sydney Travel Surveys”, 30th Australasian Transport Research Forum, 2007

724 – Longden, Thomas , “Constant Travel Budgets and Kilometres: the impact of deviations on energy use and climate policy”, Fondazione Eni Enrico Mattei, 2012

725 – Metz, David “The myth of travel time saving”, Transport Reviews, Vol. 28, No. 3, 321–336, May 2008

730 – Cervero, Robert, “Beyond travel time savings”, IBRD / World Bank, Washington USA 2011


About roadnotes

Robert Bartlett is an international consultant with over 30 years of professional experience as a highway and traffic engineer with leading companies and organisations in several countries, including Germany, China (Hong Kong), Qatar and the UK. Specialised in urban studies, transport and the use of GIS, research has included new ideas on subjects such as the study of social justice using GIS, the dimensions of vehicles, and comparative geometrics (highways and transport).
This entry was posted in project evaluation and tagged , , . Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s