它们甚至比以往的交通环道（如曼哈顿市区建于上世纪的哥伦布环道）更加高效和安全（现代设计包括使靠近环形路的车辆减速的系统，以及禁止行人进入环形的中心区域）。
(Modern designs include mechanisms for slowing traffic down as it nears the roundabouts, for example, and do not allow pedestrians onto the centre of the circle).
软盘每一面上划分成的环形区域叫作道。软盘分每面40道和80道两种。
On each side, a disk is divided into circular regions called tracks. A floppy disk has either 40 or 80 tracks per side.
各腔室在一个行程下的流体积由整个活塞组件的侧向行程和活塞的近端和远端的环形区域决定。
The flow volume per stroke of each chamber is determined by the lateral stroke of the entire piston assembly and also by the annular areas of the proximal and distal ends of the piston.
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