The Changing Allocation of Activities in Space and Time by the Use of ICT—“Fragmentation” as a New Concept and Empirical Results
Theoretical and empirical research about the impact of information and communication technologies (ICT) on transport relies on the hypothesis that ICT use leads to a reorganization of activities in time and space thus having as a consequence impacts on travel behavior. The breaking up of activities into discrete pieces by the use of ICT is the starting point of the fragmentation concept that underlies the present article. The concept argues that transport demand increases by the fragmentation of activities and explores the relevant mechanisms for this process. In all, however, the concept is still rather vague. Therefore, the authors discuss some elements of the concept on a theoretical level, in particular the question why individuals "fragment" their activities. In the empirical section they use a data set about activities, ICT use and travel behavior in Germany to find out how far an activity like work, which is particularly apt for fragmentation, shows signs of temporal and spatial disintegration. With the help of a cluster analysis they identify groups with different "fragmentation behavior" and investigate if a statistically significant relation exists between fragmentation behavior and ICT use. Accordingly, the focus of the article lies on the impact of ICT use on the performance of activities by different behavioral groups. The link to travel behavior is made by examining mode choices for different purposes and travel related attitudes.
Impact of ICT access on personal activity space and greenhouse gas production: evidence from Quebec City, Canada
This paper presents an approach to investigating the impact of information and communication technologies (ICTs) on travel behaviour and its environmental effects. The paper focuses on the spatial dispersion of out-of-home activities and travel (activity space) and greenhouse gas emissions (GHGs) at the level of the individual. An original method, combining spatial analysis in a geographic information system with advanced regression techniques, is proposed to explore these potentially complex relationships in the case of access to mobile phones and the internet, while taking into account the influence of socio-economics and built environment factors. The proposed methodology is tested using a 7-day activity-based survey in Quebec City in 2003–2004, a juncture of particular interest because these ICTs had recently crossed the threshold of 40 % (mobile phone) and 60 % (home-based internet) penetration at the time. The study period also largely pre-dates the era of mobile internet access. Among other results, socio-demographic factors were found to significantly affect both ICT access and travel out-comes. The built environment, represented by neighbourhood typologies, also played an important role. However, it was found that after controlling for the self-selection effect, built environment and socio-demographics, those who had a mobile phone available produced 30 % more GHGs during the observed week than those who did not. This higher level of GHG pro-duction was accompanied by a 12 % higher measure of activity dispersion. On the other hand, having internet access at home was associated with lower GHGs (−19 %) and lesser activity dispersion (−25 %). Possibly, mobile phones enable individuals to cover more space and produce more emissions, while the internet provides opportunities to stay at home or avoid motorized travel thus reducing emissions. The estimated effects of having a mobile phone were not only negative but also larger in magnitude from the environmental point of view than those of fixed internet access. However, the results of this study also suggest that access to mobile phones and internet may have substantial and compensatory effects at the individual level that are undetected when using model structures that do not take into account that unobserved factors may influence both ICT choices and travel outcomes.
The Vascular Theory of Migraine‐Resuscitated or More Moribund?
Your decision to publish an important paper on cerebral blood flow (CBF) in migraine1 as the first in Headache for 1989 is to be applauded. But does it clarify or cloud the issue? After 20 years of CBF studies in migraine the results show 1) a reduction of at least 25 30% in classical migraine1, 2) an average increase of 31% in common and classical migraine2, 3) or no change in common migraine3. Now we learn that the measurements need modifying by 40% to allow for scattering of radiation the Compton scatter effect which has led to "an unbalanced interpretation of the data"1 So the results are as contradictory as they can be, the measurements require adjustment, and the interpretation is therefore doubly doubtful. From the clinical point of view the neurological aura, the enlarging scotoma, the scintillations, the migration of the paraesthesiae up the arm or visual disturbances across the visual field, have not been seen in cerebrovascular disease.4 The headache is throbbing in only 47% of 750 patients questioned during a migraine5; but even when the pain is pulsatlie, it throbs for only a portion of the time at the maximum of the headache (Blau unpublished observations). The evidence for a neurological aetiology has been examined6: the most potent argument against a vascular cause is that the common triggers stress, light and hunger go direct to the nervous system, not via blood vessels. No one denies that vascular changes occur in migraine but are they primary or secondary to a neurological disturbance? Sokoloff7 concluded that the stimulated rat and monkey cortex showed increased glucose uptake, and that the increased local blood flow occurred "in response (my italics) to changes in local functional activity". The evidence, therefore, points to an underlying neurological basis with secondary vascular responses. The vascular theory may need resuscitation but who is going to give it the kiss of life?