JTH – Abstracts: 2014 – Volume 1 – Issue 3

2014 – Volume 1 – Issue 3

Excess passenger weight impacts on US transportation systems fuel use (1970–2010)


Over the past 40 years, the percentage of the US population that is overweight and obese has increased significantly, with nearly 70% of American adults now overweight or obese (National Center for Health Statistics (NCHS), 2013). The excess weight that Americans are carrying is taking a toll on the social and physical infrastructure of the country, and may also be counteracting the efforts of industries and policymakers to move towards a more energy efficient and sustainable future. This article analyzes the transportation industry to determine the amount of additional fuel use, greenhouse gas emissions, and fuel costs that are attributed to excess passenger weight in light-duty vehicles, transit vehicles, and passenger aircraft in the US from 1970 to 2010. Using driving and passenger information in the US and historical anthropometric data, it is estimated that since 1970 over 205 billion additional liters of fuel were consumed to support the extra weight of the American population. This is equivalent to 1.1% of total fuel use for transportation systems in the United States. Also, excess passenger weight results in an extra 503 million metric tonnes of equivalent carbon dioxide emissions and $103 billion of additional fuel cost over the last four decades. If overweight and obesity rates continue to increase at its current pace, cumulative excess fuel use could increase by 460 billion liters over the next 50 years, resulting in an extra 1.1 billion metric tonnes of equivalent carbon dioxide and $200 billion of additional fuel costs by the year 2060.

Can social marketing make 20 mph the new norm?


This paper reports the findings of a study that explored the possible role for social marketing in supporting compliance with 20 mph signs-only speed limits. The study, completed in July 2012, involved a review of the literature, the re-visiting of case studies of existing and planned 20 mph signs-only schemes, mainly within Great Britain, and a qualitative research project with the citizens of Bristol, England.

A key finding was the mismatch between people׳s apparent support for 20 mph limits and their actual driving behaviour. The qualitative research focused on investigating this gap. A range of groups of Bristol drivers and residents were recruited for the research to provide insights into why some people may not comply with 20 mph limits where they are in place, and what could be done to counter this non-compliance.

Effects of a Danish multicomponent physical activity intervention on active school transport


Walking and bicycling to school yields great potential in increasing the physical activity levels of adolescents, but to date very few intervention studies have been evaluated. The aim of this study was to evaluate the effect of a multicomponent school-based physical activity intervention on adolescent active school transport (AST) and three intermediate outcomes: perceived school route safety, parent support and attitude towards bicycling.


In total, 1014 adolescents at 14 schools filled in a transport diary at baseline and at a two-year follow-up and were included in the primary outcome analysis. Mean age at baseline was 12.6 years (range: 11.0–14.4 years). Seven of the schools were randomized to the intervention which was designed to change the organizational and structural environment at the schools, thereby increasing non-curricular physical activity i.e. recess activity, active transport and after-school fitness program. Transport mode to school was assessed through a 5-day transportation diary.


The proportion of active transport was high at baseline (86.0%) and was maintained at the two-year follow-up (87.0%). There was no difference in active travel between the intervention and the comparison schools after the intervention, but more students perceived parental encouragement and had a positive attitude towards bicycling at the intervention schools. This difference was however only borderline significant.


The prevalence of AST was high at both baseline and follow-up, but no difference between the intervention and comparison schools was detected. Future intervention research should ensure a high degree of involvement of students, teachers and parents, focus merely on AST and take advantage of already planned physical environment changes in well-designed natural experiments.

A biographical approach to studying individual change and continuity in walking and cycling over the life course


Most research studies seeking to understand walking and cycling behaviours have used cross-sectional data to explain inter-individual differences at a particular point in time. Investigations of individual walking and cycling over time are limited, despite the fact that insights on this could be valuable for informing policies to support life-long walking and cycling. The lack of existing longitudinal data, difficulties associated with its collection and scepticism towards retrospective methods as a means to reconstruct past behavioural developments have all contributed to this deficit in knowledge. This issue is heightened when the time frame extends to longer term periods, or the life course in its entirety. This paper proposes and details a retrospective qualitative methodology that was used to study individual change and stability in walking and cycling within a life course framework. Biographical interviews supported by a life history calendar were developed and conducted with two adult birth cohorts. Interpretive, visual biographies were produced from the interview materials. Analysis focused on identifying the occurrence, context and timing of behavioural change and stability over the life course. Typologies of behavioural development were generated to resolve common and distinct behavioural patterns over the life course. Whilst the validity of reconstructed biographies of walking and cycling cannot be proven, this is an approach which offers credible and confirmable insights on how these behaviours increase, diminish, persist, cease, are restored or adapted through the life course, and how behavioural trajectories of walking and cycling may be evolving through historical time.

High group level validity but high random error of a self-report travel diary, as assessed by wearable cameras


Self-report remains the most common method for collecting epidemiological evidence of the links between travel and health outcomes. This study assesses the validity and reliability of a self-reported travel diary (a modified version of a well-established UK travel diary; The National Travel Survey (NTS)) by comparison with wearable camera data.

Across four locations (Oxford, UK; Romford, UK; San Diego, USA; and Auckland, New Zealand) we collected 3–4 days of SenseCam (wearable camera) and travel diary data from 84 adult participants (purposive sample). Compliance with the data collection protocol was high and inspection of the crude results suggests acceptable agreement between measures for total days of data collected (diary=278; SenseCam=274), daily journey frequency (diary=4.78; SenseCam=4.64) and average journey duration in minutes (diary=17:46; SenseCam=15:40). Once these data were examined for total daily time spent travelling in minutes agreement was poorer (diary=84:53; SenseCam=72:35).

Analysis of matched pairs of journey measurements (n=1127) suggests a positive bias on self-reported journey duration of 2:08 min (95% CI=1:48–2:28; 95% limits-of-agreement=−9:10 to 13:26). Similar analysis of diary days matched to complete SenseCam days (n=201) showed a very small positive bias with a very large limits-of-agreement (1:41 min; 95% CI=−2:00 to 5:24; 95% limits-of-agreement=−50:29 to 53:41).

These results suggest self-reported journey and daily travel exposure data are relatively valid at a population level, though corrections according to reported bias could be considered. The large limits of agreement for matched journey and diary summary analysis suggest self-report diaries may be unsuitable for assessment of an individual׳s travel behaviour.

The health implications of inequalities in travel


The purpose of this paper is to examine whether some groups in society have poorer travel opportunities or are affected adversely by transport more than others with consequent implications for their health. The following potential inequalities in access to travel are considered: income, ethnicity, gender, rurality and disability. The impacts of two externalities of the transport system are considered: casualty rates and atmospheric emissions. Access to a car is found to be a key factor. Generally, the inequalities are decreasing over time as those with lower incomes increase their car ownership towards the levels of those with higher incomes.