高速公路上坡路段大車之小客車當量

PASSENGER CAR EQUIVALENTS OF LARGE VEHICLES ON FREEWAY UPGRADE SEGMENTS

進行高速公路服務水準分析時，常以大車之小客車當量（PCE）轉換實際車流成對等純小客車流，此作法並無法反應坡度、坡長及大車比例對上坡路段車流之影響。本研究以交通部運輸研究所發展之TGS模式進行模擬，分析高速公路上坡路段之車流特性，並據以估計上坡路段大車之PCE。研究發現，上坡路段之車流速率會隨著坡度、坡長及大車比例增加而降低。大車PCE隨著坡度及坡長增加呈現上升趨勢；惟當大車比例增加，大車PCE呈現下降趨勢。大車PCE在坡度2%以下時約為2.0。本研究建議分析大於2%之上坡路段時，不宜直接以一相同PCE轉換車流，而可利用TGS模式進行模擬，進而評估服務水準。

The analysis methodology of level-of-service on freeway segments usually converted real traffic flow rate to equivalent passenger-car flow by constant passenger-car-equivalent (PCE). However, it did not reflect the effect of grade, length of grade and percentage of heavy vehicle on upgrade segments. This study employed the TGS model, developed by the Institute of Transportation, to simulate the traffic condition and estimate heavy vehicle’s PCE on freeway upgrade segments. On the basis of the simulation results, this study found that average speed decreased with the increase of grade, length of grade and percentage of heavy vehicles. In addition, the PCE increased with the increase of grade and length of grade, but decreased with the increase of percentage of heavy vehicles. The PCE approximated 2.0 when the grade below 2%. Finally, this study suggested using TGS model to simulate and estimate capacity or level-of-service when grade greater than 2%, rather than convert directly the mixed traffic flow into the equivalent passenger cars by a constant PCE.