CalEnviroscreen Version 1.1 - OEHHA - State of California

CalEnviroScreen 1.1
streets near major roads in order to avoid congestion or traffic controls,
a phenomenon known as “rat-running”; this phenomenon can increase
risk of injuries among pedestrians or bicyclists in these communities.
Vehicle speed is directly associated with risk of pedestrian fatality, and
speeds along major roadways tend to be higher than normal speeds on
residential streets.
Studies have shown that non-white and low income people make up the
majority of residents in high-traffic areas (Gunier et al. 2003; Tian et al.,
2013) and that schools that are located near busy roads are more likely
to be in poor neighborhoods than those farther away (Green et al.
2004). In addition, children who live or attend schools near busy roads
are more likely to suffer from asthma and bronchitis than children in
areas with lower traffic density. This relationship has been seen in both
developed (Patel et al., 2011; Schultz et al. 2012) and developing
countries (Baumann et al., 2011).
Exposure to air pollutants from vehicle emissions has been linked to
adverse birth outcomes, such as low birth weight and preterm birth
(Ghosh et al., 2012; Ritz et al. 2007). A recent study of children in Los
Angeles found that those with the highest prenatal exposure to trafficrelated
pollution were up to 15% more likely to be diagnosed with
autism than children of mothers in the lowest quartile of exposure
(Becerra et al., 2013). The Atherosclerosis in Communities study, a cohort
study with over 15,000 participants, found that traffic density and
distance to roadways were associated with reduced lung function in
adult women (Kan et al., 2007). Road density and traffic volume were
associated with adult male mortality from cardiovascular disease in an
urban area in Brazil (Habermann and Gouveia, 2012). Motor vehicle
exhaust is also a major source of polycyclic aromatic hydrocarbons
(PAH), which can damage DNA and may cause cancer (IARC, 2010).
Method o A 150 meter buffer was placed around each of the census ZIP codes
in California. A buffer was chosen to account for roadways near ZIP
code boundaries. The selected buffer distance of 150 meters, or
about 500 feet, is taken from the California Air Resources Board Air
Quality and Land Use Handbook recommendations, which states that
most particulate air pollution from traffic drops off after
approximately 500 feet (CARB, 2005).
o The buffered boundaries were put into the Traffic Volume Linkage
Tool.
o Traffic density was calculated using two metrics from the tool: 1) the
sum of all length-adjusted traffic volumes within the buffered ZIP
code (vehicle-km/hr), then divided by 2) the sum of the length of all
road segments within the buffered ZIP code (km).
o Due to differences in the length of road segments within Highway
Performance Monitoring (HPMS), a length-adjusted traffic volumes
metric was selected. This metric multiplies traffic volumes by length of
the road segment in HPMS.
o Traffic density is calculated as traffic volumes (adjusted by road
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