Browsing by Subject "Hot spots"

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    Transport of Perfluorochemicals to Surface and Subsurface Soils
    (Center for Transportation Studies, University of Minnesota, 2013-03) Xiao, Feng; Gulliver, John S.; Simcik, Matt
    Perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA), as persistent organic pollutants, are ubiquitously present in the environment, and have been detected in human blood and breast milk at concentrations of concern to health and environmental regulators. This project aims to identify the PFOS/PFOA contamination sources, contaminant release mechanisms, and migration pathways from contaminated soils. Soil samples at different depths along and perpendicular to a U.S. highway were collected, and both compounds were regularly quantified in all of our surface soils samples (0.2–125.7 ng/g dry soil weight). The results of the surveying and sampling program and subsequently geo-statistical modeling with the aid of a Geographic Information System (GIS) identified two hot spots, and supported wind as the primary transport carrier causing the mitigation of contaminated soils from the hot spots to off-site soils. The observations indicate that PFOS and PFOA contamination is not contained to a few hot spots, but is migrating with wind and traffic to other locations. This proposed soil-to-soil migration pathway appears to be an important and heretofore overlooked migration mechanism of PFOS and PFOA from contaminated spots. We also studied their occurrence and fate in subsurface soil samples, and found a general increase in concentrations with the depth at which soil samples were collected, indicating that the contamination is also migrating toward the groundwater table.
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    United States fatal pedestrian crash hot spot locations and characteristics
    (Journal of Transport and Land Use, 2021) Schneider, Robert J.; Sanders, Rebecca L.; Proulx, Frank R.; Moayyed, Hamideh
    US pedestrian fatalities are at their highest level in nearly three decades and account for an increasing share of total traffic fatalities (16%). To achieve the vision of a future transportation system that produces zero deaths, pedestrian safety must be improved. In this study, we screened the entire US roadway network to identify fatal pedestrian crash “hot spot” corridors: 1,000-meter-long sections of roadway where six or more fatal pedestrian crashes occurred during an eightyear period. We identified 34 hot spot corridors during 2001-2008 and 31 during 2009-2016. While only five corridors were hot spots during both analysis periods, the 60 unique hot spots had remarkably consistent characteristics. Nearly all (97%) were multilane roadways, with 70% requiring pedestrians to cross five or more lanes. More than three-quarters had speed limits of 30 mph or higher, and 62% had traffic volumes exceeding 25,000 vehicles per day. All had adjacent commercial retail and service land uses, 72% had billboards, and three-quarters were bordered by low-income neighborhoods. Corridors with these characteristics clearly have the potential to produce high numbers of pedestrian fatalities. We also used hierarchical clustering to classify the hot spots based on their roadway and surrounding landuse characteristics into three types: regional highways, urban primary arterial roadways, and New York City thoroughfares. Each context may require different safety strategies. Our results support a systemic approach to improve pedestrian safety: Agencies should identify other roadway corridors with similar characteristics throughout the US and take actions to reduce the risk of future pedestrian fatalities.