of pollution from motor vehicle emissions. Section 5 explores the implications for the distributional impact of air pollution, while Section 6 extends the analysis to identification of areas where reduction of traffic congestion would have the greatest distributional benefits. Section 7 summarizes and concludes the paper.

# **2.  Prior Research**

# **2.1 Air Pollutants and Health**

This paper uses data from the European Space Agency’s Sentinel-5P platform that have been published since July 2018. Sentinel-5P measures four air pollutants that are generated by vehicular emissions: nitrogen dioxide (NO2), ozone (O3), carbon monoxide (CO) and sulfur dioxide (SO2) Extensive research has analyzed their significance as sources of health damage, with particular attention to respiratory problems for children and cardio/pulmonary problems for the elderly. For this pilot exercise, we focus on NO2, which prior research has assigned the greatest impact among the four. NO2 impacts have been extensively studied, both singly and in combination with other air pollutants (Brauer et al. 2002, 2007; Cesaroni et al. 2008; Chen et al. 2012a; Gauderman et al. 2005; Gehring et al. 2002, 2006; Hoeck et al. 2002; Morgenstern et al. 2007; Naess et al. 2007; Nafstad et al. 2004; Sunyer et al. 2006). NO2 emissions also have significance as a source of particulate matter less than 2.5 micrometers in diameter (Hodan and Barnard 2004), which is strongly associated with health problems but not measured by Sentinel-5P.

# **2.2  Modeling Traffic and Air Pollution**

Empirical research on spatial relationships between traffic and air pollution falls into three broad categories. In the first category, metropolitan-scale assessments of traffic and pollution employ engineering models calibrated for developing-country cities with plentiful information about the spatial distributions of vehicle traffic, emissions, and atmospheric conditions (Jerrett et al. 2005). For urban researchers and planners in developing countries who use these imported models, the scarcity of supporting information often requires extensive spatial and temporal interpolation to cover gaps in local data.

In the second category, local measurements of traffic and air pollution along road corridors are used to estimate vehicular emissions intensities, the local effects of meteorological variables, and the attenuation of pollution with distance from roads (Brauer et al. 2003; Gualtieri et al. 1998; Walker et al. 1999). These studies provide useful information for local zoning in developed countries. In developing-country cities, where regulatory enforcement is often difficult, they have played a useful role in promoting awareness of vehicle-based air pollution as a serious health hazard for young children and elderly adults. However, the limited scope of road corridor studies makes it difficult to extrapolate their empirical results to metropolitan scale.

The third research category has grown rapidly with the development of Geographic Information System (GIS) technology. It uses georeferenced data to assess relationships between the spatial distributions of vehicle traffic and air pollution (Briggs et al. 2010). Until recently, the spatial coverage and resolution of these studies have been greater for developed-country cities with more plentiful spatial information on vehicle traffic and air pollution. Recently, however, higher3