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V



vanpool
An organized consistent arrangement of five to 15 people traveling together and sharing the expense of the commute van.
vehicle-miles traveled (VMT)
The total distance traveled in miles in a given time period.
vertical curve
The parabolic curve connecting the two approach grades on either side of a hill.
viaduct
A series of spans carried on piers at short intervals.
visual clear (VC) zone
Used with interchange/ramp entry traffic models, this refers to the zone that provides a buffer between the driver and the end of the acceleration lane, where the driver can either merge onto the freeway in a forced maneuver or abort the merge and begin to decelerate at a reasonable rate.
vortex
A rotary, swirling, circular motion of a fluid, like wind or water, the vortex forms a vacuum at its center that draws objects toward it; examples of vortex motion are found in tornadoes and whirlpools, including the small whirlpool formed by water draining from a sink.