|ACRONYMS AND TERMINOLOGY
AADT: Annual Average Daily Traffic. The average daily traffic averaged over a full year. This value is often used for forecasting and planning highway projects.
AASHTO: American Association of State Highway and Transportation Officials. AASHTO is a nonprofit, nonpartisan association representing highway and transportation departments in the 50 states, the District of Columbia and Puerto Rico. Most notable of AASHTO's publications is "A Policy on Geometric Design of Highways and Streets" otherwise referred to as the "Green Book." Several state DOT's, including Georgia, have adopted the AASHTO Green Book as the reference guide for highway design. For more information, please visit AASHTO's website at www.aashto.org
DA: Americans with Disabilities Act
ADT: Average Daily Traffic
BMPs: Best Management Practices. Erosion and pollution control practices employed during construction to protect surface waters and/or wetlands from construction activities.
C-D Road: Collector-Distributor Road. A Collector-Distributor is a roadway that provides ingress/egress to successive crossroads that are too closely spaced to provide safe access directly to the interstate mainline. A Collector-Distributor is typically constructed parallel to the mainline and separated by either a grassed median or a concrete barrier.
CE: Categorical Exclusion. The lowest level of environmental documentation required under NEPA. It is a checklist with supporting documents as necessary.
Clear Zone: Total roadside border area, starting at the edge of the traveled way, available for safe use by errant vehicles.
Degree of Curve: The measure of the rate of change in horizontal alignment. Simply put, the higher degree of curve, the sharper the horizontal curve.
Design Year: The year in the future for which a transportation facility is designed to operate. Highway projects are designed to meet traffic projections for 20 years following construction. In addition, design year projections are made for air quality and noise.
Detention Basin: Stormwater management structure that temporarily detains runoff and discharges it through a hydraulic outlet structure to a stream or receiving water.
Easement: A tract of land necessary for the construction and/or maintenance of slopes, drainage, or other structures not contained within the right-of-way. The property owner retains ownership of land necessary for easements.
EA: Environmental Assessment. A mid-level environmental document under NEPA. It requires early coordination and much greater detail than a CE because it is required on larger more complex projects.
EIS: Environmental Impact Statement. The highest level of environmental documentation under NEPA. It is not often done unless an EA indicates that a project has serious adverse impacts.
EPD: Environmental Protection Division of the GADNR. Responsible for water quality, implementation of the state Sedimentation and Erosion Control Act of 1975, and the management of landfills throughout the state.
FEMA: Federal Emergency Management Agency. Prepares maps of flood hazard areas and administers the National Flood Insurance Program.
FHWA: Federal Highway Administration.
Flood, 100-Year: The flood water elevation that has a 1% probability of being exceeded in any given year.
Floodplain, 100-year: The area inundated by the 100-year flood.
Floodway: The channel of a river or stream plus any adjacent floodplain areas that must be kept free of encroachment (i.e., fill or structures) to avoid increasing 100-year flood elevation by more than one foot.
Fly-Over: The elevated portion of a ramp that crosses over several ramps or roadways.
FONSI: Finding of No Significant Impact. Final document in the NEPA process when an EA is complete.
GADNR: Georgia Department of Natural Resources. The SHPO, HPD, EPD, and the NHP are all within this department.
Gore: A traversable area between diverging roadways. For safety purposes, this area is typically paved for several hundred feet.
Grade: The longitudinal slope of a road, channel or natural ground. The finished surface of a canal bed, road bed, top of embankment, or bottom of excavation. Any surface prepared for the support of such things as conduit paving, ties or rails.
Limited Access: A roadway with ingress and egress fully controlled through the use of grade separated interchanges. Direct access via intersecting cross streets and business or residential driveways is prohibited.
LOS: Level of Service. A rating of roadway traffic congestion with designations "A" through "F". LOS "A" indicates absence of congestion or free traffic flow at design speed, while LOS "F" indicates a congested condition where traffic flow is seriously restricted and travel speeds are significantly below design speed.
Logical Termini: The beginning and ending points of a highway project. For Federal Aid Projects, the project must have independent utility and not require construction by other projects to achieve the project need and purpose.
NEPA: National Environmental Policy Act. Requires every federal agency to review the effect of its actions on the natural and man-made environment.
MPO: Metropolitan Planning Organization
MUTCD: Manual on Uniform Traffic Control Devices
ROW or R/W: Right-of-Way. Land owned in Fee (all land rights) for the construction and maintenance of roadways.
Section 4(f): Required by the FHWA when land will be taken from a National Evaluation Register property or a National Register eligible property or land used for public recreation for a federally funded road.
Section 404: The section of the Clean Water Act that gives the USACE the authority to regulate activities in wetlands.
Sedimentation Basin: A basin or tank in which floodwater or stormwater is retained to remove suspended matter by settling.
SHPO: State Historic Preservation Officer. The person appointed by the governor to manage historic preservation and compliance with Section 106 of the NHPA in the state. The SHPO manages the HPD and is normally a party to all MOAs.
Slope: Relative steepness of the terrain expressed as a ratio or percentage. Slopes may be categorized as positive (backslopes) or negative (foreslopes) and as parallel or cross slopes in relation to the direction of traffic.
Superelevation: The pavement cross slope measured between lane edges.
Swale: A slight depression in the ground surface where water collects and which may be transported as a stream.
TIP: Transportation Improvement Program. Road projects must be in this program to be considered for construction.
Traveled Way: Portion of the roadway for the movement of vehicles, exclusive of shoulders.
Typical Section: A drawing or description of the cross section of a road. This would usually define right-of-way limits, pavement widths, shoulder widths, ditches, medians, etc.
USACE, COE or USCOE: Army Corps of Engineers. Responsible for the implementation of Section 404 of the Clean Water Act dealing with wetlands.
USEPA: The United States Environmental Protection Agency. Has the final say in wetland permits and can reverse decisions of the USACE.
Value Engineering: Value Engineering is a technique used to evaluate life cycle costs of engineering projects. It is a standard activity undertaken by GDOT for major design projects that recommends potential cost saving opportunities to the project design team.
Weaving: The crossing of two or more traffic streams traveling in the same direction along a significant length of highway without the aid of traffic control devices. Weaving segments are formed when a merge area is closely followed by a diverge area, or when an on-ramp is closely followed by an off-ramp and the two are joined by an auxiliary lane.
Wetland Delineation: A survey conducted by a qualified person to determine the extent of wetland and the types of wetland that would be impacted by a project. To be a jurisdictional wetland, a wetland must exhibit hydrophytic vegetation, hydric soils, and wetland hydrology.