His strange habit makes sense when you consider that he's an environmental scientist who studies how to reduce litter, including things that fall off garbage trucks as they drive down the road.
Road politeness is not only good manners, but good sense too.
道路礼貌不仅是一种礼貌问题，而且还是一种良好的意识。
3
When driving in the mountains, have you ever noticed a discrepancy between the slope described on the yellow road sign and your sense that the incline is actually much steeper?