Dusty was beginning to wonder about the need for any road below when his question was answered by a caravan of heavy trucks making their way along the road. They zipped over the caravan and were gone by the time Dusty realized that air-travel was not for heavy cargo. * * * * * The buildings at the end of the aisle between the spacecraft loomed larger. The driver whipped along at his thirty-foot altitude, making no attempt to climb over the buildings which were growing taller and more massive at a frightening rate. Dusty's palms went wet; the buildings had seemed minute when they turned into the aisle, but now they were tall and massive and millions and millions of windows could be seen, with magnificent arches between the buildings spanning the gaps. The aircab whipped across an empty perimeter about the hexagonal-pattern of landing blocks, sped above a low building, and howled into the tiny space between two buildings with an arch above and a roof below, and then went into a flat climb. The car rose slowly in the canyon between the buildings that lined the street below. There were people working in those buildings, men and women that sat at their desks behind windows and paid no attention to the passage of a hundred-mile-per-hour skycab within forty feet of them. Then the car was above the roof-level but it kept to the street-lanes. Below them were the streets, and in the valley was slow-moving traffic, ground cars and air-cars that ran at different levels to avoid intersection-collisions. Up in the higher strata were the fast-moving aircabs, each moving in its lane, and each lane for a different direction. Even with separate lanes the traffic was a turmoil; constant jockeying to gain position, to avoid trouble, to move a level higher or a level lower so that a corner could be turned without entering the intersection at the wrong level. To make a right turn the driver jockeyed himself to the top of the altitude allowed that line of traffic, and in the block before his turn he rose above his lane, made his turn, and then entered the right-bound traffic pattern from below, mingling with the speeding aircabs. To make a left turn, the driver dropped to the floor of his lane, fell below, made his turn, and mingled with the left-bound turmoil from above their upper limit of altitude. They raced along in the middle-altitude at high speed; cars above them, below them, to the left and right, before and behind. "My God!" breathed Dusty, "New York at rush hour--in three dimensions." Their driver turned and winked at them. He flicked a lighter with one hand and lit the smoke that was hanging from one corner of his mouth. "Yeah man," he drawled. "Some of them guys should ought to take lessons."