Accessibility
Designing transportation systems so they can be safely and easily used by everyone, including people with disabilities, older adults, families with strollers, cyclists, and pedestrians.
Quick Summary
Whether you are attending a public meeting, reading a transportation study, following a construction project, or simply trying to understand a news report, this glossary explains terminology used throughout TranspoFairfax.
Why This Matters
Transportation decisions affect safety, travel time, neighborhood access, public spending, land use, and quality of life. Technical language should never prevent residents from understanding a proposal or contributing to a public conversation. This page helps translate professional terminology into practical community knowledge.
A
A Terms
Active Transportation
Human-powered travel, especially walking, bicycling, and the use of mobility devices.
Arterial Road
A major roadway that carries large volumes of traffic between communities and connects local streets with highways.
B
B Terms
Bicycle Facility
Infrastructure designed specifically for bicycle travel, including bike lanes, shared-use paths, bicycle boulevards, and protected cycle tracks.
Bus Rapid Transit (BRT)
An enhanced bus system designed to provide faster, more reliable service through features such as dedicated lanes, improved stations, off-board fare payment, and signal priority.
C
C Terms
Complete Streets
A transportation design philosophy that considers the needs of all users, including pedestrians, bicyclists, transit riders, motorists, and people of all ages and abilities.
Congestion
Traffic conditions where demand exceeds roadway capacity, resulting in slower travel speeds and delays.
Corridor
A roadway, rail line, transit route, trail, or broader travel area studied and managed as a connected transportation system.
D
D Terms
Dedicated Turn Lane
A lane reserved exclusively for vehicles turning left or right at an intersection.
Design Phase
The stage during which engineers prepare detailed plans, specifications, and construction drawings before a project is built.
E
E Terms
Environmental Review
A formal process used to identify and evaluate how a proposed transportation project may affect natural, historic, cultural, and community resources.
Express Lanes
Managed highway lanes that may use tolls, occupancy requirements, or both to provide a more reliable travel option.
F
F Terms
Feasibility Study
An early evaluation of whether a proposed project is practical, affordable, technically possible, and likely to meet its intended purpose.
Funding Program
A local, regional, state, or federal source of money used to plan, design, construct, operate, or maintain transportation improvements.
G
G Terms
Grade Separation
A design that places crossing transportation routes at different elevations, such as a bridge carrying a road over railroad tracks.
Greenway
A protected linear open space that may include trails and connections between neighborhoods, parks, waterways, and community destinations.
H
H Terms
High-Occupancy Vehicle (HOV) Lane
A travel lane reserved during certain times for vehicles carrying a required minimum number of occupants.
High-Occupancy Toll (HOT) Lane
A managed lane that allows qualifying carpools to travel free or at a reduced cost while other vehicles may pay a toll.
I
I Terms
Interchange
A system of ramps and bridges that allows traffic to move between two roads, usually without stopping or crossing opposing traffic.
Intersection Improvement
A change intended to improve safety or traffic operations at a roadway crossing, such as new turn lanes, signals, crosswalks, or geometry.
L
L Terms
Level of Service (LOS)
A commonly used measure describing traffic operating conditions, often expressed as grades from A through F. It is one indicator and does not by itself describe every safety, access, or community condition.
Long-Range Transportation Plan
A planning document that identifies future transportation needs, policies, and investments over a period that may extend 20 years or more.
M
M Terms
Managed Lane
A highway lane operated with rules such as tolling, vehicle occupancy, or restricted access to manage demand and improve reliability.
Microtransit
Flexible, technology-supported shared transportation that typically uses smaller vehicles and allows riders to request trips within a defined service area.
Multimodal
Involving more than one form of transportation, such as driving, transit, walking, bicycling, rail, or ferry travel.
P
P Terms
Pedestrian Facility
Infrastructure that supports walking and mobility-device use, including sidewalks, crosswalks, curb ramps, pedestrian signals, and refuge islands.
Preliminary Engineering
The early engineering work used to define a project's concept, limits, estimated cost, environmental considerations, and design requirements.
Public Participation
The process through which residents, businesses, organizations, and other stakeholders learn about and provide input on transportation plans and projects.
R
R Terms
Right-of-Way (ROW)
Land reserved for transportation purposes. Additional property sometimes must be acquired before a roadway can be widened or a trail constructed.
Roundabout
A circular intersection where vehicles travel counterclockwise around a central island, reducing severe crashes while improving traffic flow.
S
S Terms
Shared-Use Path
A wide paved trail intended for both pedestrians and bicyclists, generally separated from vehicle traffic.
Signal Timing
The programming of traffic signals to improve traffic flow, safety, and intersection efficiency.
Spot Improvement
A focused, relatively small transportation project intended to address a specific operational or safety problem.
T
T Terms
Transportation Demand Management (TDM)
Programs and strategies that reduce congestion by encouraging alternatives to driving alone, such as transit, carpooling, biking, walking, or telework.
Transit-Oriented Development (TOD)
Development planned around transit stations or major transit corridors to support walking, transit use, and a mix of nearby destinations.
Trail Connectivity
The degree to which sidewalks, shared-use paths, and trails connect neighborhoods, parks, schools, shopping areas, and transit.
U
U Terms
Utility Relocation
Moving underground or overhead utilities before roadway or trail construction begins.
V
V Terms
Vehicle Miles Traveled (VMT)
A measure of the total distance traveled by vehicles within a defined area and period of time.
Vision Zero
A transportation safety approach based on the principle that traffic deaths and serious injuries are preventable.
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