This paper analyzes the impact of uphill grades on the acceleration drivers choose to impose on their vehicles. Statistical inference is made based on the maximum likelihood estimation of a two-regime stochastic car-following model using Next Generation SIMulation (NGSIM) data. Previous models assume that the loss in acceleration on uphill grades is given by the effects of gravity. We find evidence that this is not the case for car drivers, who tend to overcome half of the gravitational effects by using more engine power. Truck drivers only compensate for 5% of the loss, possibly because of limited engine power. This indicates not only that current models are severely overestimating the operational impacts that uphill grades have on regular vehicles, but also underestimating their environmental impacts. We also find that car-following model parameters are significantly different among shoulder, median and middle lanes but more data is needed to understand clearly why this happens.

本文分析了上坡坡度对驾驶员选择施加在其车辆上的加速度的影响。基于使用下一代模拟（NGSIM）数据的两制度随机汽车跟随模型的最大似然估计，进行统计推断。以前的模型假定上坡坡度的加速度损失是由重力作用引起的。我们发现有证据表明，对于汽车驾驶员而言并非如此，他们倾向于通过使用更多的发动机功率来克服一半的重力影响。卡车司机只能赔偿损失的5％，这可能是因为发动机功率有限。这不仅表明当前的模型严重高估了坡度对常规车辆的操作影响，而且还低估了其对环境的影响。