Data from two freeway locations show that absent lane-changing, the relationships between congested speed and spacing are linear in the most congested speed ranges. The finding supports Newell’s simple car-following theory. The relationships are also found to be statistically indifferent across lanes. Moreover, speed-spacing relationships for various types of lane-changers (discretionary vs. forced due to merging and diverging) were analyzed and tested for equality. The results show that they are (statistically) indifferent from one another and also from the general relationship without lane-changing. The findings suggest that car-following behavior on a freeway can be predicted in a simple manner according to Newell’s theory, and a single general car-following model can be used without much loss of accuracy.
Samenvatting