The question of whether children's exposure to traffic-related air pollution (TRAP) contributes to their development of asthma is unresolved. We conducted a systematic review and performed meta-analyses to analyze the association between TRAP and asthma development in childhood. We systematically reviewed epidemiological studies published until 8 September 2016 and available in the Embase, Ovid MEDLINE (R), and Transport databases. We included studies that examined the association between children's exposure to TRAP metrics and their risk of 'asthma' incidence or lifetime prevalence, from birth to age 18years old. We extracted key characteristics of each included study using a predefined data items template and these were tabulated. We used the Critical Appraisal Skills Programme checklists to assess the validity of each included study. Where four or more independent risk estimates were available for a continuous pollutant exposure, we conducted overall and age-specific meta-analyses, and four sensitivity analyses for each summary meta-analytic exposure-outcome association. Forty-one studies met our eligibility criteria. There was notable variability in asthma definitions, TRAP exposure assessment methods and confounder adjustment. The overall random-effects risk estimates (95% CI) were 1.08 (1.03, 1.14) per 0.5×10-5m-1 black carbon (BC), 1.05 (1.02, 1.07) per 4μg/m3 nitrogen dioxide (NO2), 1.48 (0.89, 2.45) per 30μg/m3 nitrogen oxides (NOx), 1.03 (1.01, 1.05) per 1μg/m3 Particulate Matter <2.5μm in diameter (PM2.5), and 1.05 (1.02, 1.08) per 2μg/m3 Particulate Matter <10μm in diameter (PM10). Sensitivity analyses supported these findings. Across the main analysis and age-specific analysis, the least heterogeneity was seen for the BC estimates, some heterogeneity for the PM2.5 and PM10 estimates and the most heterogeneity for the NO2 and NOx estimates. The overall risk estimates from the meta-analyses showed statistically significant associations for BC, NO2, PM2.5, PM10 exposures and risk of asthma development. Our findings support the hypothesis that childhood exposure to TRAP contributes to their development of asthma. Future meta-analyses would benefit from greater standardization of study methods including exposure assessment harmonization, outcome harmonization, confounders' harmonization and the inclusion of all important confounders in individual studies. PROSPERO 2014: CRD42014015448.

In this paper, we present the case that traditional transport appraisal methods do not sufficiently capture the social dimensions of mobility and accessibility. However, understanding this is highly relevant for policymakers to understand the impacts of their transport decisions. These dimensions include the distribution of mobility and accessibility levels over particular areas or for specific population groups, as well as how this may affect various social outcomes, including their levels of participation, social inclusion and community cohesion. In response, we propose a method to assess the socially relevant accessibility impacts (SRAIs) of policies in some of these key dimensions. The method combines the use of underlying ethics principles, more specifically the theories of egalitarianism and sufficientarianism, in combination with accessibility-based analysis and the Lorenz curve and Gini index. We then demonstrate the method in a case study example. Our suggestion is that policymakers can use these ethical perspectives to determine the equity of their policies decisions and to set minimum standards for local transport delivery. This will help them to become more confident in the development and adoption of new decision frameworks that promote accessibility over mobility and which also disaggregate the costs and benefits of transport policies over particular areas or for specific under-served population groups.

Transport poverty is an issue that has never fully captured the interests of the transport engineering profession in either the ‘global north’ or ‘global south’ and yet it is a problem that adversely affects the daily lives of millions of people across the globe. What precisely constitutes transport poverty is not adequately articulated within academic, policy or infrastructure design literature. This paper aims to demonstrate how the different ways that academic studies and policy programmes have defined and recorded the problem of transport poverty is directly related to the ways in which it has been subsequently addressed in practice. The overall impression is one of inadequacy, fragmentation, inconsistency and tokenistic treatment of an issue that potentially affects anywhere between 10 to 90% of all households, depending on which definition is used and which country is being considered. This suggests that it is a far greater problem than the transport profession has previously been prepared to recognise and one that requires its urgent attention given the continuing trends for mass migration, urbanisation and wealth concentration within and between the ‘global north’ and ‘global south’.