Glossary of Terms
511 - A free phone service that provides real-time traffic and travel information 24 hours a day, seven days a week. Works on all cell phones and land-line phones.
Accident Investigation Sites - Designated areas away from the travel lanes to be used for temporary parking of damaged vehicles, filling out forms after an accident has occurred, emergency repair of disabled vehicles, issuing citations, etc. The purpose of these areas is to reduce "rubbernecking" and to provide a safe refuge for persons investigating an accident.
Arterial - A major highway primarily used for through traffic and usually on a continuous route; it serves major traffic movements while providing access to abutting land.
Acceleration Lane - A speed-change lane, including tapered areas, for the purpose of enabling a vehicle entering the roadway to increase its speed to a rate of which it can more safely merge into traffic.
Average Daily Traffic (ADT) - The average 24-hour volume at a given location over a defined time period less than one year.
Annual Average Daily Traffic (AADT) - The average 24 hour volume at a given location over a full 365 day year.
Average Annual Weekday Traffic (AAWT) - The average 24-hour volume occurring on weekdays over a 365 day year.
Barrier Walls - Concrete walls used in the median or between two adjacent roadways in order to prevent vehicles from crossing into oncoming traffic and to redirect errant vehicles.
Bicycle Lane or Bike Lane - A portion of a roadway that has been designated by striping, signing and pavement markings for preferential or exclusive use of bicycles.
Capacity - The maximum hourly rate at which persons or vehicles can be reasonably expected to traverse a point or a uniform section of a lane or roadway during a given time period under prevailing roadway, traffic, and control conditions.
Changeable Message Sign - Electronic sign capable of displaying any message as programmed by the operator to inform motorists of any situation which would cause traffic delays or necessitate the use of an alternate route.
Collector Distributor Road - A limited access road adjacent to an interstate and similar to a frontage road which collects traffic from the interstate and distributes it to various roads with exits located along that interstate. It also collects the traffic wishing to enter the interstate from the various roads along the interstate and distributes it onto the main line of the interstate at a single point.
The Clean Air Campaign - The Clean Air Campaign is a non-profit organization that works to reduce traffic congestion and improve air quality through a variety of voluntary programs and services. It serves as a clearinghouse for a multitude of organizations that have programs in place to address traffic congestion and air pollution.
Daily Vehicle Miles Traveled (DVMT) - A daily average of the amount of vehicle miles traveled (VMT) on Georgia's public roads.
District - A management region defined by the Georgia DOT; the Department's seven district offices throughout the state provide localized services.
Deceleration Lane - A speed-change lane which enables a vehicle exiting from a roadway to slow to the safe turning speed of the intersection or driveway it is approaching.
Environmental Protection Agency (EPA) - A federal agency charged with protecting the natural resources of the nation.
First Responder - The company or unit who is expected to reach the scene of an incident first.
Flashing Beacon - Overhead flasher which is installed in an area where a traffic signal is not warranted but where some warning of a hazardous condition is needed. A yellow flashing beacon indicates the use of caution and a red flashing beacon serves as a stop sign.
Freeway - An expressway with full access control.
Frontage Road - A street or road auxiliary to and located on the side of an expressway or freeway for service to abutting property and for control of access.
Georgia Rideshare Program - Transportation program that provides a safe and convenient way to commute to Ride lots.
Governor's Road Improvement Program (GRIP) - A system of four-lane highways that enhance economic development throughout the state. It was initiated in 1989 by a resolution of the state legislature and the Governor to connect 95 percent of our state's cities (with a population of 2,500 or more) to the Interstate System.
Gore - The area created between two sections of roadway (not median) and includes Gore Left and Gore Right.
GRTA - The Georgia Regional Transportation Authority.
Guardrail - Lengths of metal rails located along the roadway designed to prevent vehicles from entering a hazardous zone by deflecting the vehicle away from the hazard. Also used to prevent the crossing of the median on some divided highways.
HERO Units (Highway Emergency Response Operators) - Georgia DOT employees who respond quickly to incidents and clear the roads so that the normal traffic flow can be restored. Responsible for patrolling the Atlanta-area freeways. Provide support to law enforcement, first responders and other emergency agencies. The HERO's primary duty is to minimize the disruption of traffic caused by major incidents. Operators patrol all the designated routes to assist with incidents and stranded motorists. These operators, who are sometimes the first on the scene of an accident, are trained in emergency first aid, crash vehicle extrication and recognition of hazardous materials. Their vehicles are fully equipped with emergency materials such as fuel transfer tank, air compressors, 200- ft air tube, directional arrow board, flashing lights, portable generator and push-bumpers.
High Occupancy Vehicle (HOV) or Express Lane - Lanes which are designated only for vehicles with two or more passengers (excluding commercial trucks). Approximately 90 lane-miles of HOV lanes operate on I-75, I-85 and I-20 24 hours a day, seven days a week in the following areas:
  • I-75 inside I-285 (Cobb, Fulton, and Clayton counties)
  • I-75/I-85 (Downtown Connector)
  • I-85 between Brookwood Interchange and SR 20 / Buford Dr. (Exit 115) - DeKalb and Gwinnett counties
  • I-20 east of I-75/I-85 (Downtown Connector) - Fulton and DeKalb counties
High Occupancy Toll (HOT) Lane - Limited-access managed lanes that allow eligible carpoolers, transit, motorcycles and Alternative Fuel Vehicles to use lane for free, while allowing previously ineligible solo drivers to buy back into the lane for a fee. The number of cars using these lanes can be controlled through value pricing via electronic toll collection so as to maintain free-flowing traffic in them at all times, even during the height of rush hours.
Highway Directional Terms -
EB = Eastbound
WB = Westbound
NB = Northbound
SB = Southbound
Intelligent Transportation Systems (ITS) - Initiatives by government and industry to improve safety, mobility, efficiency, productivity and environmental quality of transportation systems through the use of modern electronics and communications technologies.
Interstate - A freeway that is part of the Dwight D. Eisenhower National System of Interstate and Defense Highways (the Interstate System); a divided highway which can be accessed only by on and off ramps.
Local Assistance Road Program (LARP) - The Georgia resurfacing program designed to assist local governments in preserving their paved road systems.
Lane Designation - Assignment of a number to each lane on a multi-lane or divided highway beginning with lane #1 as the closest to the center of the roadway and moving with progressively higher number for each lane to the right. Lanes in Georgia are always numbered left to right.
Loop Detector - Coil of wire embedded in the roadway used to detect vehicle volume/presence. This data enables a traffic signal to function more efficiently, programming changes from red to green based on demand. Also used to control ramp meters.
MARTA - The Metropolitan Atlanta Rapid Transit Authority.
Median - The portion of a divided highway separating the traveled ways for traffic moving in opposite directions.
Mile Post - Markers located on interstate highways and state routes which denote the distances from the Georgia state line on the interstate routes and the distances from the adjoining county line on other state routes. Distances run south to north and west to east.
National Highway System (NHS) - A network consisting of the interstates and other specifically designated routes which provide access to major intermodal facilities and to key military bases.
NaviGAtor - Georgia's integrated Intelligent Transportation System designated to minimize congestion of highways and improve traveler safety within the metro Atlanta area.
Park & Ride Lots - Transit access mode in which passengers drive or bicycle to a transit station, park in a specified area and ride the transit system from there to their destination.
Ramp Meter - Traffic signal devices located on entrance ramps to the interstate, which regulate the frequency of vehicles entering the traffic stream on a freeway.
Rest Area - A public facility, located next to a large thoroughfare such as a highway, expressway, or freeway at which drivers and passengers can rest, eat or refuel without exiting onto secondary roads.
Right-of-Way (ROW) - The land acquired for or devoted to transportation purposes; for example, highway ROW and railroad ROW.
Raised Pavement Marker - Reflector located on the lane lines of the roadway to better define each lanes under limited light conditions.
Right-of-Way - A general term denoting land, property or interest therein, usually, but not required to be, in a strip, acquired for or devoted to a highway and its appurtenant structures.
Shoulder - The portion of the roadway contiguous with the traveled way for accommodations of stopped vehicles, for emergency use and for lateral support of base and surface courses.
Statewide Transportation Improvement Plan (STIP) - A list of federally-funded, priority transportation projects proposed to be carried out in the first three years of adoption. The Office of Planning oversees the STIP public involvement process for the six rural Georgia DOT Districts.
Surface Transportation Assistance Act of 1982 (STAA) - A highway program that designates national routes for oversized trucks to move freight throughout the state.
Transportation Control Centers (TCC) - Satellite transportation management facilities that are linked directly to the TMC, establishing a regional transportation management system.
Transportation Demand Management (TDM) Program - A program that focuses on reducing the number of single occupancy vehicles on the road. These projects include trip reduction programs such as carpooling, vanpooling or teleworking.
Transportation Management Center (TMC) - The facility located in the Wayne Shackelford Building that houses Georgia's NaviGAtor system.
Vehicle Miles Traveled (VMT) - The number of miles traveled nationally by vehicles for a period of 1 year.
Warning Signs - Warning signs are used to inform drivers of upcoming hazards that they might not see or otherwise discern in time to react safely.
Welcome Center - A tourist information center providing visitors to a location with information on the area's attractions, lodgings, maps and other items relevant to tourism. Often, these centers are operated at the airport or other port of entry by the local government or chamber of commerce. Often a visitor center is called simply an information center.