【答案解析】The traffic forms on land depend on more consideration of the aspect of politics, economy and environment than technology. Currently we can construct more solid, tranquil and skidproof road, but we don't do it because of high expenditure. We can install celotex on both sides of highway and design truck with little tail gas and tire of low noise to reduce half traffic noise. However, we are unwilling to pay out for it. environmentally-friendly canvasser has exercised great influence over auto manufacturers so that they have been much more strict with the control of tail gas emission. However, we still take up a heavy responsibility and a long course in the aspect of air pollution control.