Peer-Reviewed Publications

Determinants of black carbon, particle mass and number concentrations in London transport microenvironments
Ioar Rivas, Prashant Kumar, Alex Hagen-Zanker, Maria de Fatima Andrade, Anne Dorothee Slovic, John P. Pritchard, Karst T. Geurs
Atmospheric Environment, 161 (2017), pp. 247-262
Abstract: We investigated the determinants of personal exposure concentrations of commuters’ to black carbon (BC), ultrafine particle number concentrations (PNC), and particulate matter (PM1, PM2.5 and PM10) in different travel modes. We quantified the contribution of key factors that explain the variation of the previous pollutants in four commuting routes in London, each covered by four transport modes (car, bus, walk and underground). Models were performed for each pollutant, separately to assess the effect of meteorology (wind speed) or ambient concentrations (with either high spatial or temporal resolution). Concentration variations were mainly explained by wind speed or ambient concentrations and to a lesser extent by route and period of the day. In multivariate models with wind speed, the wind speed was the common significant predictor for all the pollutants in the above-ground modes (i.e., car, bus, walk); and the only predictor variable for the PM fractions. Wind speed had the strongest effect on PM during the bus trips, with an increase in 1 m s−1 leading to a decrease in 2.25, 2.90 and 4.98 μg m−3 of PM1, PM2.5 and PM10, respectively. PM2.5 and PM10 concentrations in car trips were better explained by ambient concentrations with high temporal resolution although from a single monitoring station. On the other hand, ambient concentrations with high spatial coverage but lower temporal resolution predicted better the concentrations in bus trips, due to bus routes passing through streets with a high variability of traffic intensity. In the underground models, wind speed was not significant and line and type of windows on the train explained 42% of the variation of PNC and 90% of all PM fractions. Trains in the district line with openable windows had an increase in concentrations of 1 684 cm−3 for PNC and 40.69 μg m−3 for PM2.5 compared with trains that had non-openable windows. The results from this work can be used to target efforts to reduce personal exposures of London commuters.
Exposure to air pollutants during commuting in London: Are there inequalities among different socio-economic groups?
Ioar Rivas, Prashant Kumar, Alex Hagen-Zanker
Environment International, 101 (2017), pp. 143-157
Abstract: People with low income often experience higher exposures to air pollutants. We compared the exposure to particulate matter (PM1, PM2.5 and PM10), Black Carbon (BC) and ultrafine particles (PNCs; 0.02–1 μm) for typical commutes by car, bus and underground from 4 London areas with different levels of income deprivation (G1 to G4, from most to least deprived). The highest BC and PM concentrations were found in G1 while the highest PNC in G3. Lowest concentrations for all pollutants were observed in G2. We found no systematic relationship between income deprivation and pollutant concentrations, suggesting that differences between transport modes are a stronger influence. The underground showed the highest PM concentrations, followed by buses and a much lower concentrations in cars. BC concentrations in the underground were overestimated due to Fe interference. BC concentrations were also higher in buses than cars because of a lower infiltration of outside pollutants into the car cabin. PNCs were highest in buses, closely followed by cars, but lowest in underground due to the absence of combustion sources. Concentration in the road modes (car and bus) were governed by the traffic conditions (such as traffic flow interruptions) at the specific road section. Exposures were reduced in trains with non-openable windows compared to those with openable windows. People from less income-deprived areas have a predominant use of car, receiving the lowest doses (RDD < 1 μg h− 1) during commute but generating the largest emissions per commuter. Conversely, commuters from high income-deprived areas have a major reliance on the bus, receiving higher exposures (RDD between 1.52 and 3.49 μg h− 1) while generating less emission per person. These findings suggest an aspect of environmental injustice and a need to incorporate the socioeconomic dimension in life-course exposure assessments.
Air quality in the megacity of São Paulo: Evolution over the last 30 years and future perspectives
Maria de Fatima Andrade, Prashant Kumar, Edmilson Dias de Freitas, Rita Yuri Ynoue, Jorge Martins, Leila D. Martins, Thiago Nogueira, Pedro Perez-Martinez, Regina Maura de Miranda, Taciana Albuquerque, Fabio Luiz Teixeira Gonçalves, Beatriz Oyama, Yang Zhang
Atmospheric Environment, 159 (2017), pp. 66-82
Abstract: We present a comprehensive review of published results from the last 30 years regarding the sources and atmospheric characteristics of particles and ozone in the Metropolitan Area of São Paulo (MASP). During the last 30 years, many efforts have been made to describe the emissions sources and to analyse the primary and secondary formation of pollutants under a process of increasing urbanisation in the metropolitan area. From the occurrence of frequent violations of air quality standards in the 1970s and 1980s (due to the uncontrolled air pollution sources) to a substantial decrease in the concentrations of the primary pollutants, many regulations have been imposed and enforced, although those concentrations do not yet conform to the World Health Organization guidelines. The greatest challenge currently faced by the São Paulo State Environmental Protection Agency and the local community is controlling secondary pollutants such as ozone and fine particles. Understanding the formation of these secondary pollutants, by experimental or modelling approaches, requires the description of the atmospheric chemical processes driven by biofuel, ethanol and biodiesel emissions. Exposure to air pollution is the cause of many injuries to human health, according to many studies performed not only in the region but also worldwide, and affects susceptible populations such as children and the elderly. The MASP is the biggest megacity in the Southern Hemisphere, and its specifics are important for other urban areas that are facing the challenge of intensive growth that puts pressure on natural resources and worsens the living conditions in urban areas. This text discusses how imposing regulations on air quality and emission sources, mainly related to the transportation sector, has affected the evolution of pollutant concentrations in the MASP.
Potential impacts of bike-and-ride on job accessibility and spatial equity in São Paulo
John P. Pritchard, Diego Bogado Tomasiello, Mariana Giannotti, Karst Geurs
Transportation Research Part A: Policy and Practice, 121 (2019), pp. 386-400
Abstract: This paper examines the potential of the bicycle, as an access mode for transit trips, to reduce spatiotemporal inequalities in job accessibility in the megacity of São Paulo, Brazil. Three temporally dynamic potential job accessibility models are developed, (i) a GTFS-based (General |Transit Feed Specification) walk-and-ride model, (ii) an integrated GTFS-based bike-and-ride model that incorporates topography constraints, the availability of dedicated cycling infrastructure, waiting times at intersections and car traffic levels, and (iii) a car model that accounts for congestion using TomTom speed profiles. Cluster analysis is then used to analyze the geographic distribution of the associated improvements. The results show that bike-and-ride has the potential to substantially increase job accessibility in the different areas of the city, but does not result in a more equal spatial distribution of job accessibility, as measured by Gini coefficients. Most of the improvements are centered in middle to high income areas with good accessibility. Peripheral areas, that tend to be the poorest and have the lowest accessibility by transit, improve the least. The inclusion of the bicycle is not enough to counteract all of the other forces causing low job accessibility in these areas.
An international comparison of equity in accessibility to jobs: London, São Paulo and the Randstad
John P. Pritchard, Diego Bogado Tomasiello, Mariana Giannotti, Karst Geurs
Transport Findings, 1 (2019), pp. 1-12
Abstract: We analyze the impact of different accessibility measures on the interpretation of associated equity analysis using the Gini Coefficient and the (pseudo) Palma Ratio, and the impact of the method of assigning zonal accessibility on Gini estimation results using four different alternatives. Two types of potential accessibility measures (zonal and person-based) and two ratios of potential jobs to potential population (intra-modal and multi-modal) are estimated for car and transit in the Netherlands’ Randstad region, Greater London, and São Paulo relying on network data, schedule-based data, and speed profiles. Gini results are heavily influenced by the accessibility indicator and the method of assignment. The Palma ratio is also influenced by the choice of accessibility indicator, with the person-based potential accessibility measure tending to show greater inequity.
Impact of route choice and period of the day on cyclists' exposure to black carbon in London, Rotterdam and São Paulo
Veronika Sassen Brand, Prashant Kumar , Aline Santos Damascena, John P. Pritchard, Karst Geurs, Maria de Fatima Andrade
Journal of Transport Geography, 76 (2019), pp. 153-165
Abstract: Cyclists are exposed to direct traffic emissions due to their proximity to on-road vehicles. Several studies associate black carbon (BC) exposure with both mortality and morbidity caused by cardiovascular and respiratory diseases. We did a comparative assessment of cyclists' exposure to BC in three cities: London, Rotterdam and São Paulo. We measured personal exposure to BC during the peak and off-peak hours in all three cities using the same instrument. Three origin-destination (O-D) pairs, each with two routes, for a total of six routes, were chosen in each city. The first route of each O-D pair was along busy major roads and the other perceived to be clean passing close to green/blue/quiet areas. This work brings together results from three different Latin American and European cities, with an aim to understand the BC exposure variabilities while cycling during peak and off-peak hours, identify main pollution hotspots resulting in enhanced exposure and associate the measured concentrations with proximity to green areas and waterways. BC concentrations were higher during the morning- peak hours compared with evening-peak hours in Rotterdam and São Paulo. London showed an opposite trend, with higher concentrations during evening hours. In most cases, the cyclists using the alternative route were found to be less exposed to BC in London and São Paulo. In Rotterdam, the differences in absolute concentrations between main and alternate routes were modest. Each city is different but the common features among all were that the exposure is related to route choice, a period of the day and proximity with the mobile sources. These findings have implications in terms of considering the pollutants exposure when establishing new cycle routes.
Equity Analysis of dynamic bike-and-ride accessibility in the Netherlands
John P. Pritchard, Marcin Stepniak, Karst Geurs
In K. Lucas & K. Martens with F. Di Ciommo & A. Dupont-Kieffer (Eds.), Measuring Transport Equity. Elsevier.
Abstract:This chapter analyzes spatiotemporal variations in job accessibility in the Netherlands, with a particular focus on bike-and-ride accessibility. This alternative incorporates cycling as both a potential access mode and an alternative to public transport. The accessibility provided by the bike-and-ride model is compared to the private car and the walk-and-ride model (public transport with pedestrian access and egress). In order to capture a more nuanced view of the accessibility conditions, the walk-and-ride and bike-and-ride models rely on general transit feed specification (GTFS) data to incorporate the temporal variability of public transport travel times. In the case of the car, speed profiles that account for network congestion are used. All three of these door-to-door potential accessibility models use temporally disaggregated travel time estimations in 15-minute intervals for 24 hours. From an egalitarian perspective of justice, the outcome of the bike-and-ride integration is explored. The improvements in accessibility are analyzed at the national and city level and Gini coefficients are used to measure the distributional impacts of the accessibility improvements. The main conclusion is that bike-and-ride is effective in providing better job accessibility for public transport users in the Netherlands. In doing so, it also reduces the distributional inequality of the accessibility provided by the public transport system and lowers the modal gap in accessibility between the car and public transport.