AADT
Annual Average Daily Traffic. The estimated average number of vehicles using a roadway each day over a full year.
Quick Summary
Transportation agencies frequently use abbreviations to identify organizations, laws, funding programs, project phases, and technical concepts. This guide explains the acronyms most likely to appear in Fairfax County and Northern Virginia transportation discussions.
Why This Matters
Acronyms can make public information feel inaccessible. Understanding a few recurring abbreviations makes it much easier to follow project timelines, compare funding sources, read staff reports, and participate confidently in community meetings.
A
A Acronyms
ADA
Americans with Disabilities Act. Federal civil-rights law requiring accessible transportation facilities, programs, and services.
B
B Acronyms
BRT
Bus Rapid Transit. Enhanced bus service designed for faster, more reliable travel through features such as dedicated lanes, improved stations, and signal priority.
C
C Acronyms
CIP
Capital Improvement Program. A multi-year plan for funding major public facilities and infrastructure.
CTB
Commonwealth Transportation Board. The Virginia board that oversees statewide transportation policy and funding decisions.
D
D Acronyms
DRPT
Virginia Department of Rail and Public Transportation. The state agency supporting rail, transit, commuter assistance, and related transportation programs.
E
E Acronyms
EA
Environmental Assessment. A study used to determine whether a proposed project may cause significant environmental effects.
EIS
Environmental Impact Statement. A detailed federal environmental review for projects that may significantly affect the human or natural environment.
F
F Acronyms
FCDOT
Fairfax County Department of Transportation. The county department responsible for transportation planning, programs, coordination, and many local project initiatives.
FHWA
Federal Highway Administration. The federal agency that supports highways, bridges, roadway safety, and related programs.
FTA
Federal Transit Administration. The federal agency that supports public transportation systems and transit capital projects.
H
H Acronyms
HOT
High-Occupancy Toll. Managed lanes that allow qualifying carpools to travel free or at a reduced charge while other vehicles may pay a toll.
HOV
High-Occupancy Vehicle. A vehicle carrying the minimum number of occupants required to use a designated lane or receive another travel benefit.
I
I Acronyms
ITS
Intelligent Transportation Systems. Technology used to improve traffic operations, traveler information, safety, and system management.
L
L Acronyms
LOS
Level of Service. A commonly used measure describing traffic operating conditions, often graded from A through F.
M
M Acronyms
MPO
Metropolitan Planning Organization. A federally required regional body that coordinates long-range transportation planning and funding in an urbanized area.
MUTCD
Manual on Uniform Traffic Control Devices. The national standard for traffic signs, signals, pavement markings, and other roadway control devices.
N
N Acronyms
NEPA
National Environmental Policy Act. The federal law requiring environmental review and public disclosure for many federally funded or permitted projects.
NVTA
Northern Virginia Transportation Authority. The regional authority that plans and funds major transportation improvements across Northern Virginia.
NVTC
Northern Virginia Transportation Commission. A regional body that coordinates and supports public transit policy and funding in Northern Virginia.
P
P Acronyms
PE
Preliminary Engineering. The early engineering work used to define a project, evaluate alternatives, estimate costs, and prepare it for final design.
R
R Acronyms
ROW
Right-of-Way. Land reserved, owned, or acquired for a transportation facility such as a road, rail line, sidewalk, or trail.
RRFB
Rectangular Rapid Flashing Beacon. A pedestrian-activated flashing warning device used at some crosswalks.
S
S Acronyms
SMART SCALE
Virginia transportation prioritization program. Virginia’s process for scoring and ranking eligible transportation projects competing for state funding.
SRTS
Safe Routes to School. Programs and improvements that help children walk and bicycle to school more safely.
STIP
Statewide Transportation Improvement Program. Virginia’s federally required short-range program of transportation projects using federal funds or requiring federal approval.
SUP
Shared-Use Path. A path designed for multiple users, commonly including people walking, bicycling, and using mobility devices.
SYIP
Six-Year Improvement Program. Virginia’s six-year program identifying transportation projects scheduled for development or construction.
T
T Acronyms
TAC
Transportation Advisory Commission. A citizen advisory body that provides transportation guidance and recommendations to Fairfax County leaders.
TDM
Transportation Demand Management. Strategies that reduce single-occupant vehicle travel through transit, ridesharing, telework, walking, bicycling, and flexible schedules.
TIP
Transportation Improvement Program. The metropolitan region’s short-range, financially constrained list of federally supported transportation projects.
TOD
Transit-Oriented Development. Compact, walkable development planned around high-capacity transit.
TPP
Transportation Priorities Plan. A plan used to identify, evaluate, and sequence transportation investment priorities.
TRV
Transforming Rail in Virginia. Virginia’s statewide passenger and freight rail improvement initiative.
V
V Acronyms
VDOT
Virginia Department of Transportation. The state agency that owns, operates, and maintains most public roads in Fairfax County.
VMT
Vehicle Miles Traveled. The total number of miles traveled by vehicles in a defined area and period.
VPRA
Virginia Passenger Rail Authority. The state authority responsible for advancing and managing Virginia’s passenger rail investments.
VRE
Virginia Railway Express. Northern Virginia’s commuter rail service connecting suburban communities with Alexandria, Crystal City, and Washington.
W
W Acronyms
WMATA
Washington Metropolitan Area Transit Authority. The regional agency that operates Metrorail, Metrobus, and MetroAccess.
Where You Will Encounter These Acronyms
They commonly appear in county staff reports, VDOT project pages, environmental studies, public hearing notices, funding applications, Board of Supervisors materials, regional plans, construction updates, and community presentations.