Transportation Engineering Glossary
25 essential terms — because precise language is the foundation of clear thinking in Transportation Engineering.
Showing 25 of 25 terms
The American Association of State Highway and Transportation Officials, which publishes design standards and guidelines for highways and bridges in the United States.
The total volume of traffic passing a point or segment of a highway in both directions over a 24-hour period, averaged over a year.
A soil strength test comparing penetration resistance of a sample to that of standard crushed stone, used in pavement design.
Streets designed to accommodate all users including motorists, transit riders, bicyclists, and pedestrians safely.
Vehicles with communication (V2V, V2I) and/or automated driving capabilities that will reshape transportation infrastructure.
The traffic density at which flow reaches its maximum (capacity). Beyond this point, congestion occurs.
The maximum safe speed for a roadway section under favorable conditions, governing geometric feature selection.
A standard unit quantifying pavement damage from vehicle axle loads relative to an 18,000-pound single axle.
Pavement using asphalt layers over aggregate base, distributing loads through the layer system.
The design of roadway physical features including alignment, cross-section, sight distance, and intersection layout.
The maximum sustainable traffic flow rate on a roadway under prevailing conditions.
The TRB publication providing standard methodologies for evaluating highway and street operations and level of service.
The application of advanced technologies to transportation for real-time monitoring, control, and communication.
A qualitative measure of traffic conditions graded A (free flow) through F (breakdown), used to evaluate facility performance.
The engineering process of determining pavement layer thicknesses and materials to withstand traffic and environmental loads.
Traffic signals on freeway on-ramps that regulate the rate of vehicles entering the mainline to maintain flow.
Pavement using Portland cement concrete slabs that distribute loads over a wide area through beam action.
A circular intersection with yield-at-entry that reduces conflict points and the severity of crashes.
A boundary between two traffic states that propagates through the traffic stream, explaining congestion propagation.
The roadway length visible to a driver. Types include stopping, passing, and decision sight distance.
The distance required for a driver to perceive a hazard, react, and stop. Combines perception-reaction and braking distances.
The banking of a roadway on horizontal curves to counteract centrifugal force on vehicles.
The mathematical study of the relationships among flow, density, and speed in a traffic stream.
The determination of green, yellow, and red intervals for signal phases to optimize operations.
A measure of total distance traveled by all vehicles in a given area over a specified period, used in planning and safety analysis.