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The number of vehicles occupying a unit length of a highway at a given instant. It directly affects the level of service and is measured in vehicles per mile or kilometer.

The time or distance between two successive vehicles traveling in the same direction on a given path, which influences capacity and safety considerations.

The traffic volume during the highest one-hour period of the day. It is crucial for identifying congestion periods and planning for peak load management.

A qualitative measure describing operational conditions within a traffic stream. It ranges from A (free flow) to F (breakdown flow).

The number of vehicles that pass a point on a highway over a specific time period, often expressed in vehicles per hour (vph).

A phenomenon where a sudden change in traffic conditions, such as a lane reduction or an accident, causes a ripple effect of slowed or stopped traffic upstream.

The maximum hourly rate at which persons or vehicles can be reasonably expected to traverse a point or uniform section of a lane or roadway during a given time period under prevailing roadway, traffic, and control conditions.

The maximum flow rate possible at a signalized intersection during a green phase under prevailing traffic conditions, typically measured in vehicles per hour of green time.

The number of vehicles lined up on a roadway due to congestion or control delays, extending from a stopping point or reducing flow location.

Mathematical models that describe how a driver maintains a safe following distance behind another vehicle, a critical aspect for traffic simulation and analysis.

A mathematical relationship given by $Q = k \times v$, where $Q$ is the flow rate, $k$ is the density, and $v$ is the average speed of the traffic stream.

The average speed of vehicles on a given road segment when the roadway is not affected by congestion or traffic control measures.

The average speed of all vehicles occupying a particular segment of roadway at a given instant, important for understanding flow characteristics.

The flow of vehicles over a specific section of road at a given time, which can be analyzed in terms of flow, speed, and density.

A section of highway that experiences a reduction in capacity and flow quality, often due to physical or operational constraints, leading to congestion.

The average speed of a series of vehicles passing a point on a highway over a defined period of time.

The total volume of vehicle traffic of a highway for a year divided by 365 days. AADT is a useful indicator for traffic flow and road usage.

Circular intersections designed to facilitate the flow of traffic without the use of traffic signals, reducing conflict points and typically improving capacity and safety.

The unobstructed, traversable roadside area that allows a driver to stop safely or regain control of a vehicle that veers out of the travel lane.

The use of traffic signals at freeway entrance ramps to control the rate at which vehicles enter the flow of traffic, improving traffic stability and reducing congestion.

A series of traffic lights coordinated to allow continuous traffic flow over several intersections in one main direction, optimizing traffic progress and efficiency.

Advanced applications designed to provide innovative services relating to different modes of transport and traffic management, enhancing safety and lowering congestion.

The section of roadway where vehicles merge, diverge, or cross paths, typically found at interchange ramps and causing complicated traffic interactions affecting capacity.

Signs, signals, pavement markings, and other devices placed on roadways to regulate, warn, or guide road users, impacting flow rate and capacity.

Strategies and policies aimed at reducing traffic congestion by adjusting travel behavior, transportation modes, or times of travel, affecting highway capacity usage.

An engineering technique where roads cross without direct intersection, commonly by using overpasses or underpasses, improving traffic flow and safety.

A study assessing the effects that a new development or change in land use may have on the surrounding transportation system, including road capacity.

A set of urban design strategies intended to slow down or reduce motor vehicle traffic, thus improving safety for pedestrians and cyclists.

Additional traffic that arises due to increased road capacity, typically resulting from an expanded highway system or improved infrastructure.