Further, in this analysis, higher levels of road variables were linked to lower levels of hopanes.
By the early 1990s a significant proportion of BS emissions in the UK were from traffic-related sources, but the model presented here does not include any road variables.
(18) Buffers of 0.5, 1, 2, and 3 km were applied to road variables and 0.5, 1, 2, 3, 4, 5, 7.5, and 10 km buffers were applied to land cover and population, and 24 variables in domains of road, landcover, population, x-y trend, and altitude were considered.
"Buffering", using ArcGIS FOCALSUM with the circle option (subsequently referred to as buffers), was used to sum the contribution (i.e., area or length) of each land cover and road variable around each monitoring site, based on the 100 m grids.
For example, the two additional Class 3 variables were highly negatively correlated with the distance to Class 3 roads variable (ρ = -0.62 and ρ = -0.67 for 200 m and 400 m, respectively), and the traffic-weighted road-length within 100 m was highly correlated with the total traffic density within 100 m (ρ = 0.96).
Colonias, developed from subdivided agricultural lands in response to a deficit in low-income housing [ 4], are substandard residential areas often with inadequate roads, variable housing conditions, and limited access to safe water and sewer sources [ 5]. Almost 20% of these largely Mexicano households have a female head, and 50% of children are food insecure [ 6, 7].
The challenges are similar across developing nations, where little is known about the relationship between pedestrian crashes, traffic flow, and road environment variables on rural two-way roads, and where unique predictor variables may be needed to capture the unique crash risk circumstances.
Second, after only one spatial scale was selected for each landscape variable, we evaluated pairwise correlations among the nest site, landscape, and distance to nearest road explanatory variables using Pearson correlation.
Soil pH decreased from 7.0 to 4.3, and extractable-Ca from 18.3 to 0.6 cmol+/kg, with increasing distance from the road; both variables were significantly higher at the roadside than at distances of 25 and 50 m.
Finally, these road length variables were weighted by the wind rose data, creating a wind-weighted traffic proxy.
While our NO2 data have been validated, 19 we were not able to assess the validity of our road proximity variables.
