Evolution of trip based mode share of travellers aged 20 to 29 (source Kuhnimof et al)

A forthcoming study* to be published in the journal Transport Reviews casts more light on Gen Y’s reluctance to take up driving with the same alacrity their parents and grandparents did at the same age.

I’ve discussed aspects of this issue before (here, here and here). However this paper is especially interesting for a number of reasons.

One is it compares the travel behaviour of young adults across six industrialised countries in three continents, so we can see how universal and how varied the change is. It also examines trends in driving by young adults over a long time frame i.e. the last 30 years.

Further, the research differentiates by a number of important variables, like sex, enabling us to see if that’s got any value as an explanatory variable. It measures the number of licensed drivers aged in their twenties, their access to a car, their use of other modes, and the total kilometres they travel by all modes.

The authors (T Kuhnimhof, J Armoogum, R Buehler, J Dargay, J Denstadli and T Yamamoto) rely mainly on travel survey data. They compare Germany, France, Great Britain, Norway, Japan and the USA.

It’s important to stress at the outset that this sort of exercise is fraught because of data limitations. The methodology of travel surveys differs between countries; the years in which the surveys were conducted vary by country; and there are only a small number of data points i.e. mostly one per decade per country.

The authors have made efforts to “harmonise” the various surveys. Even so, they emphasise the trends – the direction of change – rather than the absolute levels of each variable at any time. Having said that, even with limitations, formal studies are most times a big improvement on “intuition” (or prejudice).

Although there’s considerable variation between countries, the researchers confirm the generally accepted understanding that young adults aged 20-29 are travelling less than the same cohort did just prior to the new millennium.

Total kilometres travelled by this age group (for convenience, I’ll call them millennials) fell in all countries between the nineties and the noughties. However what’s especially interesting is the extent of the fall differed – it was only marginal in Norway and Japan, modest in France, but very large in Germany, Great Britain and, especially, in the US.

Another key finding is that millennial men turned away from driving in greater numbers than millennial women. Travel by males fell markedly in five countries over the same period (although not in all countries – young men now drive more in Norway).

Kilometres driven by millennial women also fell. However the fall in women’s driving was generally smaller than that for men and wasn’t observed in all countries. In particular, there was barely any change in France and Japan.

One consequence is that American and German women of this generation now drive as much as their male counterparts. This is a turnaround from the nineties when men in those countries drove noticeably more.

While it’s not true of all countries, most show a similar downward trend in the number of millennials who have a driver’s license.

In the 1990s, young men were more likely to have a license than young women in all the countries studied. This has reversed in Germany and the USA, and has almost levelled out in most other countries.

Millennials’ access to cars also declined. The authors employ the concept of “car availability” – it’s positive if a person has a driver’s license and lives in a household with at least one car.

With the exception of Japan, there was no country in which car availability of young adults in total was higher after 2005 than before the turn of the millennium. In Norway and France a noticeable decline of car availability even occurred throughout the 1980s and 1990s. The decrease after 2000 is specifically pronounced in Germany, Norway and Great Britain.

The mode share of cars fell over the period in all countries, most dramatically in Germany (see exhibit). Conversely, public transport’s share of total travel by millennials rose in five countries – again especially in Germany – but not in the US.

A particularly interesting issue examined in the paper is “modality”. This variable seeks to capture the extent to which millennials rely on multiple modes rather than just one.

For planners and policy makers it is important to understand if the decline in the car mode share is mainly caused a) by an increased share of travellers with few alternatives (i.e. carless households or ‘transit captives’) or b) by travellers with multiple options who increasingly choose not to use the car. The latter (b) would indicate that the alternatives, specifically public transport, are increasingly competitive in a multioptional market.

They find a long-term trend toward increasing multimodality on the part of millennial car owners is only important in Germany and Great Britain. It is especially important in Germany though, where the shift to other modes explains around a third of the decrease in car travel between 1998 and 2008.

In Germany, and to a lesser extent in Great Britain, the decline in driving by millennials has been offset by an increase in use of alternative modes, primarily public transport. However in France, Japan and (especially) the US, this has not been the case – the decline in driving has resulted in an overall fall in travel.

The authors’ primary interest is in measuring millennials’ behaviour rather than explaining it (I’ve looked at that question before, herehere and here). Still, they make it clear they think broad social changes are the primary explanation for the travel trends they identify. In the case of Germany, they say, structural forces account for two thirds of the reduction in driving.

They cite factors like more young adults in tertiary education, lower workforce participation, and starting families at a later age, as contributing to “a larger share of young people being in a life situation in which they are less prone to car ownership or use.” Incidentally, they think smart phones have negligible impact.

Yet it’s not just socioeconomic and technological change. Kuhnimhof et al say policy measures aimed at discouraging driving and promoting use of alternative modes also shape millennials’ travel behaviour.

They refer to the introduction of the ‘semesterticket’ in Germany. It provides a large discount on public transport for students and appears to have led to a significant increase in mode share. They say the shift of travel demand by car owners to other modes in Germany explains around a third of the decrease in young adults’ travel between 1998 and 2008.

The size of the decline in driving and overall travel (depending on the country) identified by the authors has obvious implications for policy. I think there’re other important takeaways from this research, though.

Most of the change appears to be the result of wider social/structural forces. Urban policy-makers needs to recognise and understand that. They should “work with the grain”, not against it or in ignorance of it.

There are important differences between countries on a number of variables. Even where the direction of the outcome is the same across countries, the route to it is often a combination of differently-weighted factors.

As always, policy-makers must be very careful about borrowing from elsewhere. What holds for Germany (say) won’t necessarily or even probably hold elsewhere. But then again it might, so it’s important to look outwards.

*Note: one of the authors gave me an advance copy of the paper. Sorry, I’m not permitted to pass on copies.