First is free flow in which the density of traffic is low enough to allow vehicles to travel at the maximumspeed allowed.
首先是畅通无阻,交通密度足够低,使得车辆能以最高时速行驶。
2
The Segway, which has a maximumspeed of 12.5mph and can travel around 18 miles between charges, was unveiled by New Hampshire entrepreneur Dean Kamen 2001 and went on sale the following year.