Patterns of traffic activity, including changes in the volume and speed of vehicles, vary over time and across urban areas and can substantially affect vehicle emissions of air pollutants. Time-resolved activity at the street scale typically is derived using temporal allocation factors (TAFs) that allow the development of emissions inventories needed to predict concentrations of traffic-related air pollutants. This study examines the spatial and temporal variation of TAFs, and characterizes prediction errors resulting from their use. Methods are presented to estimate TAFs and their spatial and temporal variability and used to analyze total, commercial and non-commercial traffic in the Detroit, Michigan, U.S. metropolitan area. The variability of total volume estimates, quantified by the coefficient of variation (COV) representing the percentage departure from expected hourly volume, was 21, 33, 24 and 33% for weekdays, Saturdays, Sundays and holidays, respectively. Prediction errors mostly resulted from hour-to-hour variability on weekdays and Saturdays, and from day-to-day variability on Sundays and holidays. Spatial variability was limited across the study roads, most of which were large freeways. Commercial traffic had different temporal patterns and greater variability than noncommercial vehicle traffic, e.g., the weekday variability of hourly commercial volume was 28%. The results indicate that TAFs for a metropolitan region can provide reasonably accurate estimates of hourly vehicle volume on major roads. While vehicle volume is only one of many factors that govern on-road emission rates, air quality analyses would be strengthened by incorporating information regarding the uncertainty and variability of traffic activity.

中文翻译：

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在整个城市地区分配年度交通活动时的时空变化及其对空气质量评估的影响。

交通活动的模式（包括车辆的体积和速度的变化）会随时间推移以及在整个城市地区变化，并且会严重影响车辆的空气污染物排放。通常，使用时间分配因子（TAF）得出街道规模上的时间分辨活动，该时间分配因子可用于开发预测与交通相关的空气污染物浓度所需的排放清单。这项研究检查了TAF的时空变化，并描述了由于使用它们而导致的预测误差。提出了估算TAF及其时空变异性的方法，并用于分析美国密歇根州底特律都会区的总，商业和非商业交通。总交易量估算的可变性，工作日，周六，周日和节假日的变异系数（COV）表示偏离预期每小时小时数的百分比分别为21％，33％，24％和33％。预测错误主要是由于工作日和周六的每小时变化以及周日和节假日的每日变化。研究道路上的空间变异性有限，其中大多数是大型高速公路。与非商业车辆相比，商业流量具有不同的时间模式和更大的可变性，例如，每小时商业量的平日可变性为28％。结果表明，大城市地区的TAF可以合理准确地估算主要道路上的每小时车辆通行量。车辆数量只是控制公路排放率的众多因素之一，