A city (or county) is not an accident but the result of coherent visions and aims
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- Potential strategies to avoid and mitigate health impacts near roadways
- Infill development and active transportation create numerous co–benefits
- Strategy Description of research findings Appropriate context other considerations I. Strategies that reduce traffic emissions
- III. Strategies that remove pollution from the air breathed by people
- Sample Policy Example of Application Relationship to Other Elements
C H A P T E R 4 : R E Q U I R E D E L E M E N T S | 191 4 The Atlanta, Georgia Summer Olympic games of 1996 provides an example of a holistic approach to improve air quality through temporary mitigation strategies. Recognizing there would be an influx of people, Atlanta implemented a suite of policies to accommodate the additional visitors in a clean and travel efficient manner. These included a 24-hour public transit system, additional buses, modified work place policies such as telecommuting, and even adjustments to delivery schedules. Researchers were able to evaluate the impact of these short-term policies and showed decreased ozone, traffic counts, and acute care asthma visits. Although these were temporary measures, they reflect of what a more comprehensive suite of policy objectives could achieve through mode shift from car dependency to alternative forms of transit. Just as in the Atlanta games example, the suite of strategies to address near roadway land use must be considered as it applies to the local context. Potential strategies to address near-roadway land use are identified below. Process strategies are listed to consider during the general plan update process. Additionally, mitigation strategies are identified for cases when they are needed. The mitigation measures listed are based on a review of the literature conducted by the Air Resources Board and published in the Strategies to Reduce Air Pollution Exposure Near High-Volume Roadways . Potential strategies to avoid and mitigate health impacts near roadways Process Strategies Aimed at identifying, mitigating, and avoiding—if possible— exposure to air pollution. • Consult with regional air district during early stages of the general plan update when prioritizing areas for infill development to identify stationary and mobile sources of toxic air contaminants • Consult with regional air district, community, and other stakeholders during identification of potential infill sites and create an inventory • Engage with local community members early in the general plan update process to discuss vision, local priorities, and concerns • Engage with local community groups working on related issues early in the general plan update • Incorporate air pollution reduction goals and exposure reduction goals into the general plan language • Prioritize discussion of policy goals that have the potential to reduce emissions overall to be incorporated into the general plan policy language, such as reduction of lanes in roads • Prioritize discussion of policy goals that support mode shift from single occupancy vehicles to transit and/or active transit to be incorporated into the general plan policy language Infill development and active transportation create numerous co–benefits Image by Urban Advantage, Dover Kohl & Partners C H A P T E R 4 : R E Q U I R E D E L E M E N T S | 192 4 Mitigation Strategies Mitigation strategies are aimed at identifying various potential strategies that cities and counties can incorporate as needed to reduce exposure to near-roadway pollution. Locating potential infill development sites near a high volume roadway may yield an array of benefits, which should be balanced with drawbacks associated with near roadway pollution. Additionally, many communities already have sensitive land uses near which can not be easily relocated, and thus need mitigation strategies to reduce health impacts. Research over the last decade has identified mitigation strategies that reduce pollution concentrations, emissions, or improve air flow. Site-specific factors should be carefully considered as local jurisdictions, in conjunction with their regional air district, assess and select mitigation strategies that make the most sense for the local context. Also, as illustrated with the 1996 Atlanta games example, a combination of mitigation strategies is likely to have a greater impact than implementing one stand-alone measure. The research on mitigation measures tends to fall into one of several categories including: 1. Strategies to reduce traffic emissions 2. Strategies to increase dispersion of traffic pollution 3. Strategies to remove pollution from the air breathed by people A full discussion of mitigation strategies and the background research is available in the Air Resources Board Technical Advisory: Strategies to Reduce Air Pollution Exposure Near High-Volume Roadways . The table below is a high level summary of the description of the strategy, the research findings, and appropriate context and other considerations. Please consult the full publication for a more in-depth discussion. Strategy Description of research findings Appropriate context & other considerations I. Strategies that reduce traffic emissions 1. Speed Reduction Mechanisms, including roundabouts Vehicle speed reduction mechanisms change the design and operating speed of the road by altering the physical characteristics of the road. These features can reduce stop-and-go driving and hard accelerations and thereby reduce emissions rates. Some of these features, like the roundabout intersection, can be used as an alternative to stop-controlled and signalized intersections. Studies show that roundabouts can reduce localized pollutant concentrations compared to intersections with stop and signal control by 20% or more (depending on context and site-specific conditions). Transportation planners and engineers should carefully consider the potential direct and indirect effects of imple- menting speed reduction mechanisms to determine if they will reduce vehicle emissions and other impacts to the environment as well as to traveler safety and delay. When guidance is needed to estimate emissions and air qual- ity-related effects, planners and engineers may consult with MPOs or traffic modeling experts. 2. Traffic Signal Management Traffic signal management systems can reduce stop-and- go driving and vehicle idling, resulting in reduced localized pollutant concentrations of up to 50% compared to corridors that do not implement these systems. Studies show that site-specific conditions dictate the magnitude of reductions. Many different types of signal management are available, and planners should identify what is best for air quality, vulnerable road user safety, and transit and active mode throughput and comfort. 3. Speed limit reductions on high-speed roadways (>55 mph) Research studies have identified an optimal average speed range of ~35-55 mph within which per-mile traffic emissions and fuel consumption are minimized. Gener- ally, speed limit reductions on high-speed roadways can reduce tailpipe emission rates up to 30%, depending on the change in speed, the pollutant measured or modeled, and the roadway characteristics. Speed limit reductions are appropriate on roadways where speed limit and design speeds exceed 55 mph. C H A P T E R 4 : R E Q U I R E D E L E M E N T S | 193 4 Strategy Description of research findings Appropriate context & other considerations II. Strategies that increase dispersion of traffic pollution 4. Design that promotes ventilation along street corridors The physical layout of urban streetscapes influences air flow and pollution movement. Research studies show that street corridors characterized by buildings with varying shapes and heights, building articulations (street frontage design elements like edges and corners that help break up building mass), and spaces that encourage air flow (e.g., parks) benefit from better pollutant dispersion and air quality. For example, buildings of varying heights can result in significant increases in turbulence (e.g., up to doubling), and adding bike lanes and sidewalks not only reduces car traffic, but also creates space for more dispersion (up to a 45% reduction in particulate concen- trations). Wider sidewalks, bicycle lanes, and other features ben- efitting pedestrians can also create space for better air flow and pollutant dispersion along with increasing active transportation and mode shift. This strategy should be considered in the context of the overall need to increase development density. 5. Solid barriers and walls Measurement and modeling studies consistently find that solid barriers reduce near-road downwind concentrations by increasing vertical dispersion of pollutants emitted by vehicles. The magnitude of the reduction and its spatial extent depend on the height of the barrier, the width of the road, and micrometeorology. As reference, studies have consistently found that pollution concentrations downwind of the barrier, ranging from 10% to 50% reduc- tion compared to concentrations measured on or directly adjacent to high-volume roadways. Solid barriers should only be considered for installation along freeways, because they have the negative effect of dividing neighborhoods and obscuring sightlines. 6. Vegetation for pollutant dispersion Studies indicate that vegetation has the potential to alter pollutant transport and dispersion. In some studies, specific locations and conditions translated to air quality benefits (e.g., pollution concentrations of up to 20% on the leeward side of the tree line). It should be noted that most studies were conducted on the East Coast and in Europe where vegetation types and densities differ from what is found in California. Online tools are available to assist with the selection of appropriate vegetation considering allergen impacts, watering needs, and other factors. Maximum benefits have been shown to occur when vegetation is combined with solid barriers. III. Strategies that remove pollution from the air breathed by people 7. Indoor high efficiency filtration Studies show that particle filtration systems and devices, specifically high-efficiency filtration with mechanical ventilation or portable high efficiency air cleaners, can be highly effective for reducing indoor pollution concentra- tions. High efficiency filters in ventilation systems can remove from 50-99% of particles in the air. However, research shows that filtration technologies for gaseous pollutants (VOCs) are variable in their effectiveness; some remove certain VOCs well, but not others. Planners should be aware of current state and local build- ing codes and their respective air filtration requirements, including requirements for amending code standards. Regular operation and maintenance is necessary for highest filter and ventilation efficiency, and is required by regulation in commercial buildings. Near roadway siting considerations and strategies will continue to evolve. For example, vehicles will continue to become cleaner over the coming years, changing the balance in benefits and drawbacks of near roadway development. A general plan update provides a platform on which to consider multiple policy options simultaneously, and the opportunity to create holistic, internally consistent solutions. C H A P T E R 4 : R E Q U I R E D E L E M E N T S | 194 4 OPR Recommended Policies These policies are an example of recommended policies adopted by varying jurisdictions, to be modified and used as appropriate. A full list of recommended policies can be found here. Sample Policy Example of Application Relationship to Other Elements [City, county] shall require that new multi-family residen- tial buildings and other sensitive land uses in areas with high levels of localized air pollution be designed to achieve good indoor air quality through landscaping, ventilation systems, or other measures. City of Murrieta Land use, housing, healthy communities [City, county] shall provide incentives to promote air pollution reductions, including incentives for developers who go above and beyond applicable requirements and mitigate pollution for facilities and operations that are not otherwise regulated. City of Chula Vista Land use, healthy communities, environmental justice [City, county] shall require uses such as smog check stations, automotive painting and repair facilities conduct such activities in enclosed and filtered spaces to prevent odors and emissions from affecting passers-by, nearby residents, and building occupants National City Healthy communities, environmental justice [City, county] shall employ strategies in the Community Design Element that reduce driving rates and improve air quality through land use and urban design will be implemented by the City and other responsible parties. These strategies include transit-oriented development, compact development, an appropriate mix of land uses, a jobs/housing balance, transit oriented development, and walkable streets. City of Southgate Circulation, land use, economic development, healthy communities [City, county] shall minimize exposure to air pollution and hazardous substances County of Ventura Climate change, environmental justice, healthy communities [City, county] shall encourage non-polluting industry and clean green technology companies to locate to the City. City of Murrietta Climate change, environmental justice, economic development, healthy communities Document Outline
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