Investigation of roadside fine particulate matter concentration surrounding major arterials in five Southern Californian cities.

The built environment surrounding arterials affects the dispersion of vehicular emissions in urban areas, modifying the potential risks to public health. In order to study the influence of urban morphometry on flow and dispersion of vehicular fine particulate matter emissions, in the summer of 2008 field measurements were performed in major arterials located in five Southern Californian cities with different building geometries. In each city, local mean wind, turbulence, virtual temperature, roadside DustTrak Fine Particles (DTFP) concentration, and traffic flow data were collected in 2-hr measurement periods during morning and evening rush hours and lighter midday traffic, over a period of 3 days. The calculated Monin-Obukhov length, L, suggests that near-neutral and slightly unstable conditions were present at both street and roof levels. The nondimensional forms of turbulent wind and temperature fluctuations show,that the data at street level within the urban canopy can be represented using the Monin-Obukhov similarity theory. Generalized additive models were applied to analyze the impact of meteorological and traffic-related variables on fine particle concentrations at street level Compared to other variables, urban-scale background concentrations were the most important variables in all five models. The results confirmed that turbulent mixing in urban areas dominated the variation of roadside particle concentrations regardless of urban geometry. The distance from the local sites to the nearby monitoring stations affected model performance when urban-scale concentrations were used to predict middle-scale concentrations by generalized additive models (GAMs). A radius ofinfluence for background concentrations was 6-10 km. There were also relationships between concentration and other variables affecting the local components of the concentrations, such as wind direction, sensible heat flux, and vertical wind fluctuation, although the influences were much weaker Implications: The built environment surrounding major arterials affects the dispersion of vehicular emissions in urban areas, modifying the potential risks to public health. Dispersion of pollutants within the urban canopy is governed by flow and turbulence characteristics caused by building morphometry. Current dispersion models used for regulatory purposes have difficulties simulating the flow and dispersion for complex building cases, especially when fine resolution is needed. Urban planning strategies, such as limitation of building height, pedestrian-friendly community design, or zoning of building structures, modify concentrations of vehicular emissions in built environments surrounding major arterials, which may modify health risks for adjacent communities.

Retrofitting the suburbs to increase walking: evidence from a land-use-travel study.

This paper reports results from a detailed travel diary survey of 2125 residents in the South Bay area of Los Angeles County - a mature, auto-oriented suburban region. Study areas were divided into four centres, typical of compact development or smart growth, and four linear, auto-oriented corridors. Results show substantial variation in the amount of walking across study areas. Trips are shorter and more likely to be via walking in centres. A key to the centres' increased walking travel is the concentration of local shopping and service destinations in a commercial core. Yet the amount of business concentration that is associated with highly pedestrian-oriented neighbourhoods is from three to four times as large as what can be supported by the local resident base, suggesting that pedestrian-oriented neighbourhoods necessarily import shopping trips, and hence driving trips, from larger surrounding catchment areas. The results suggest both land use and mobility strategies that can be appropriate for suburban regions.

The Irvine-Minnesota inventory to measure built environments: reliability tests.

BACKGROUND: Inter-rater reliability is an important element of environmental audit tools. This paper presents results of reliability tests of the Irvine-Minnesota Inventory, an extensive audit tool aimed at measuring a broad range of built environment features that may be linked to active living. METHODS: Inter-rater reliability was measured by percentage agreement between observers. Reliability was tested on a broad range of sites in both California and Minnesota. RESULTS: For the variables that remained in the inventory, in tests conducted at the University of California-Irvine, 76.8% of the variables had >80% agreement among the three raters. In tests conducted at the University of Minnesota, 99.2% of the variables had >80% agreement among the two raters. CONCLUSIONS: Reliability was high for most items. The inventory was modified to eliminate items with low reliability. Differences in the use of the inventory and the goals of the research led to generally higher reliability in Minnesota. Those differences, limitations, and directions for future research are discussed.

Evaluation of the California Safe Routes to School legislation: urban form changes and children's active transportation to school.

BACKGROUND: Walking or bicycling to school could contribute to children's daily physical activity, but physical environment changes are often needed to improve the safety and convenience of walking and cycling routes. The California Safe Routes to School (SR2S) legislation provided competitive funds for construction projects such as sidewalks, traffic lights, pedestrian crossing improvements, and bicycle paths. METHODS: A cross-sectional evaluation examined the relationship between urban form changes and walking and bicycle travel to school. Surveys were distributed to parents of third- through fifth-grade children at ten schools that had a completed SR2S project nearby. Two groups were created based on whether parents stated that their children would pass the SR2S project on the way to school or not. RESULTS: Children who passed completed SR2S projects were more likely to show increases in walking or bicycle travel than were children who would not pass by projects (15% vs 4%), based on parents' responses. CONCLUSIONS: Results support the effectiveness of SR2S construction projects in increasing walking or bicycling to school for children who would pass these projects on their way to school.

How the built environment affects physical activity: views from urban planning.

The link between the built environment and human behavior has long been of interest to the field of urban planning, but direct assessments of the links between the built environment and physical activity as it influences personal health are still rare in the field. Yet the concepts, theories, and methods used by urban planners provide a foundation for an emerging body of research on the relationship between the built environment and physical activity. Recent research efforts in urban planning have focused on the idea that land use and design policies can be used to increase transit use as well as walking and bicycling. The development of appropriate measures for the built environment and for travel behavior is an essential element of this research. The link between the built environment and travel behavior is then made using theoretical frameworks borrowed from economics, and in particular, the concept of travel as a derived demand. The available evidence lends itself to the argument that a combination of urban design, land use patterns, and transportation systems that promotes walking and bicycling will help create active, healthier, and more livable communities. To provide more conclusive evidence, however, researchers must address the following issues: An alternative to the derived-demand framework must be developed for walking, measures of the built environment must be refined, and more-complete data on walking must be developed. In addition, detailed data on the built environment must be spatially matched to detailed data on travel behavior.