根據我國環保署資料顯示，移動源為都市地區最重要之污染源，其中以柴油車輛所排放之廢氣最為嚴重，其排放之空氣污染物，因含有金屬、有機物、酸化物等，所以會對人體健康與環境造成莫大的危害，故我國環保署於民國76年開始對柴油車實施排放煙度之管制，將煙度標準訂為50%，再陸續降低標準至現在的15%，以降低柴油車所排放之空氣污染物。本研究彙整歷年南投縣動力計檢測站及路邊攔檢柴油車輛之各項資料後發現，民國94年度至103年度於南投縣動力計檢測站中，以第二期排氣煙度標準下之柴油車輛數較多，且整體平均動力計全負載煙度有下降之趨勢，及其排氣煙度合格率平均為93%，合格率逐年上升中。另民國95年度至103年度於南投縣路邊攔檢中，以第三期排氣煙度標準下之柴油車輛數較多，且整體平均路攔無負載煙度有下降之趨勢，及其排氣煙度合格率平均為84%，合格率逐年上升中。從這些柴油車廢氣排放結果證明南投縣空氣品質已獲得改善。

According to statistics of the Taiwan Environmental Protection Agency（TEPA）, the exhaust emissions of diesel vehicles are the principal sources of air pollution for moving vehicles in urban areas of Taiwan. These emissions contain materials such as metals, organics, and acidifying substances, which are harmful to human health and the environment. Therefore, in 1987, the TEPA began to manage and control the exhaust emissions of diesel vehicles, setting a standard to reduce smoke emissions to 50% and gradually lowering the standard to 15%. This study compared smoke emissions of Nantou County’s diesel vehicles, tested roadside and at the Nantou EPB’s testing station. From 2005 to 2014, at the Nantou EPB’s testing station, diesel vehicles with a full load were mostly categorized according to the exhaust range for the second term standard. These results showed that the average smoke emissions of fully loaded diesel vehicles followed a downward trend. Overall, the exhaust-smoke pass rate, which increased yearly, was 93%. Diesel vehicles tested roadside without a load during 2006–2014 were mostly categorized according to the exhaust range for the third term standard, with the results of average smoke emissions for these vehicles also following a downward trend. The average exhaust-smoke pass rate, which increased yearly, was 84% for these vehicles. These exhaust emission results for diesel vehicles in Nantou County demonstrate improved air quality.