Traffic Density in California
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The CalEnviroScreen is a mapping tool developed by the California Office of Environmental Health Hazard Assessment to identify communities in California (at the census tract level) that are most affected by pollution sources. The tool uses indicators to measure environmental conditions. Traffic density is an exposure indicator, which measures the different types of pollution people may come into contact with. From CalEnviroScreen: What is Traffic Impacts? California has the biggest network of freeways in the country. Its cities are known for heavy traffic. Traffic impacts is a measure of the number of vehicles on the roads in an area. Non-whites, Latinos, low income people, and people who speak a language other than English often live in or near areas with high traffic. Why is this indicator included in CalEnviroScreen? While California has strict vehicle-emissions standards, exhaust from cars and trucks is the main source of air pollution in much of the state. Major roads and highways can bring air pollutants and noise into nearby neighborhoods. Exhaust fumes contain toxic chemicals that can damage DNA, cause cancer, make breathing difficult, and cause low weight and premature births. Children who live or go to schools near busy roads have higher rates of asthma and other lung diseases than children in areas farther from roads. What measure is used in CalEnviroScreen 4.0 to evaluate traffic impacts? The indicator uses information on the amount of traffic on major as well as some local roads and the length of the roads in or near each census tract. Traffic impacts is calculated by dividing the traffic volumes by the total road length for the year 2017. A complete description of the Traffic Impacts indicator can be found in the CalEnviroScreen 4.0 report. Where can I find more information about traffic and health? OEHHA: Air Pollution from Nearby Traffic and Children’s Health Harvard School of Public Health: Emissions from traffic congestion may shorten lives
CalEnviroScreen是由加州环境健康危害评估办公室（California Office of Environmental Health Hazard Assessment）开发的制图工具，旨在以人口普查街区（census tract）为基本单元，识别加利福尼亚州内受污染源影响最为严重的社区。该工具通过多类指标量化评估环境状况，其中交通密度属于暴露指标，用于衡量人群可能接触到的各类污染类型。 摘自CalEnviroScreen官方内容：何为交通影响（Traffic Impacts）？加利福尼亚州拥有全美规模最大的高速公路网络，其城市亦以拥堵交通闻名。交通影响（Traffic Impacts）指标用于衡量某一区域道路上的车辆通行总量。非白人、拉丁裔、低收入群体以及非英语母语人群，往往聚居在高交通流量区域或其周边地带。 为何该指标会被纳入CalEnviroScreen？尽管加利福尼亚州制定了严苛的机动车排放标准，但汽车与卡车的尾气仍是该州多数区域的首要空气污染源。主干道与高速公路会将空气污染物与噪声带入周边社区。尾气中含有有毒化学物质，可损伤DNA、诱发癌症、引发呼吸困难，还会导致低体重儿与早产。居住在繁忙道路附近或就近就学的儿童，其哮喘及其他肺部疾病的发病率显著高于远离道路区域的儿童。 CalEnviroScreen 4.0采用何种方式评估交通影响（Traffic Impacts）？该指标采集各人口普查街区范围内及周边的主干道与部分地方道路的车流量及道路长度数据。交通影响（Traffic Impacts）得分以2017年的车流量除以道路总长度计算得出。关于交通影响（Traffic Impacts）指标的完整说明可查阅CalEnviroScreen 4.0官方报告。 如何获取更多与交通及健康相关的信息？ 加州环境健康危害评估办公室（OEHHA）：《周边交通造成的空气污染与儿童健康》 哈佛大学公共卫生学院：《交通拥堵排放物或缩短人类寿命》
