为探究川藏高原梯度带海拔高度与线形条件对高速公路轻型车CO₂排放的影响，采用便携式车辆排放测试系统在汶川-马尔康高速公路开展往返程实车试验，分析车辆比功率、CO₂排放速率以及排放因子的变化规律，建立车辆CO₂排放因子与坡度的关联模型。结果表明：海拔对排放有影响，且差异明显，根据排放影响特征，可将试验路段海拔分为1 400~2 250 m和2 250~3 240 m两个范围；海拔2 250~3 240 m CO₂排放速率较1 400~2 250 m降低约40%，两段海拔范围的CO₂排放速率分布均值分别为1.5 g/s与2.5 g/s；同一海拔范围内，圆曲线半径在［1 100 m, 1 400 m］的CO₂排放因子分布均值较半径小于1 100 m更小；海拔1 400~2 250 m内不同坡度区间CO₂排放因子分布均值随坡度的增大呈先增大后减小的趋势，极差为21 g/km；海拔2 250~3 240 m不同坡度区间CO₂排放因子分布均值随坡度的增大呈S型增长趋势，极差为53 g/km。

To explore the influences of altitude and alignment conditions along the gradient zone of the Sichuan-Tibet Plateau on CO₂ emissions of light-duty vehicles on expressways, a portable emission measurement system was employed to conduct round-trip real-vehicle tests on the Wenchuan-Barkam Expressway. The variation patterns of vehicle specific power, CO₂ emission rate, and CO₂ emission factor were analyzed. Moreover, correlation models between vehicle CO₂ emission factor and grade was established. The results indicate that altitude has a significant influence on emissions. Based on the emission influence characteristics, the altitude of the test section can be divided into two ranges: 1 400 ~ 2 250 m and 2 250 ~ 3 240 m. The CO₂ emission rate in the altitude range of 2 250 ~ 3 240 m is approximately 40% lower than that in the range of 1 400 ~ 2 250 m. The mean values of CO₂ emission rates in these two altitude ranges are 1.5 g/s and 2.5 g/s respectively. Within the same altitude range, the mean value of CO₂ emission factors for circular curves with a radius in[1 100 m, 1 400 m] is smaller than that for curves with a radius less than 1 100 m. In the altitude range of 1 400 ~ 2 250 m, the mean value of CO₂ emission factors in different grade intervals initially increases and then decreases with the increase of grade, with a range of 21 g/km. In the altitude range of 2 250 ~ 3 240 m, the mean value of CO₂ emission factors in different grade intervals exhibits an S-shape growth trend as the grade increases, with a range of 53 g/km.