Basic Freeway Section-- Freeway segments that are outside of the influence of ramps or weaving sections.
Capacity-- The maximum number of vehicles that can reasonably be expected to traverse over a specific section of roadway, in one direction, during a given time period and under the prevailing conditions. This is expressed in passengers cars per hour per lane (pcphpl).
Design Conditions-- The physical qualities of a basic freeway section such as lane width, shoulder clearances and density of interchanges (on and off ramps).
Density-- The number of vehicles in a one-mile segment of one lane of traffic.
Flow rate-- The rate, in vehicles per hour or passenger cars per hour, at which traffic traverses a freeway segment.
Free-flow speed-- The speed of traffic flow that is unaffected by upstream or downstream conditions. Ideally, free-flow speed is the speed that occurs when density and flow are zero.
Level of Service (LOS)-- A measure of the operating conditions of a basic freeway section. There are six categories A through F with F being the least desirable.
Peak-hour factor-- The ratio of the number of vehicles during the peak hour to four times the number of vehicles entering the traffic stream during the peak 15-minute period.
Traffic conditions-- The qualities of traffic such as traffic speed, density, vehicle types and traffic flow rate.
V/C ratio-- The proportion of the facilitys capacity being utilized by current or projected traffic. v/c = rate of flow/capacity.