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Adopt-A-Highway program
A volunteer program organized to keep Idaho roads and highways litter-free. Groups, organizations or individuals volunteer to clean two-mile segments at least twice a year. More

Aggressive driving
Not to be confused with road rage, which is a deliberate and violent act against another driver and is a criminal offense. The behaviors that define aggressive driving are:
  1. failing to yield right of way
  2. passing a stop sign
  3. speeding
  4. driving too fast for conditions
  5. tailgating
  6. disregarding a traffic signal

Alternative fuels
Low-polluting fuels which are used to propel a vehicle instead of high-sulfur diesel or gasoline. Examples include methanol, ethanol, propane or compressed natural gas, liquid natural gas, low-sulfur or "clean" diesel and electricity.

Arterial highway A major thoroughfare, used primarily for through traffic rather than for access to adjacent land, that is characterized by high vehicular capacity and continuity of movement.

Section of roadway leading to a bridge.

Arch culvert
Bridge feature that resembles the top half of a large tube. The arch shape makes it easier for fish to swim down the creek that passes under the arch.

Average Daily Traffic (ADT)
The total traffic volume during a given period (from 1 to 364 days) divided by the number of days in that period.

Backcountry airstrips
The Division of Aeronautics owns and maintains 30 backcountry airports and airstrips that serve recreational and resource management needs of remote Idaho locations.

Booster seat
A booster seat is recommended for children who have outgrown child safety seats. Children who fit that description should be properly restrained in booster seats in the back seat until they are at least 8 years old or more than 4 feet 9 inches tall. A booster seat positions a child up so a safety belt can fit correctly. Without a booster seat, a small child can be ejected from a vehicle in a crash. More

Any structure carrying vehicles or pedestrians over an obstacle or depression. For ITD, it includes all overpasses, on-ramps, small bridges over streams, etc.

Bridge deck
The road surface of a bridge.

Bureau of Transportation Statistics (BTS)
BTS has an intermodal transportation focus with a mission to compile, analyze, and publish statistics relevant to the nations transportation system. Created to improve the knowledge base for public decision-making and to improve public awareness of the nation's transportation system, BTS collects information on transportation and other areas as needed. The Bureau's largest data collection programs are the Commodity Flow Survey and the American Travel Survey, conducted jointly with the Bureau of the Census to identify where freight and people go by all modes of transportation. More

A roadway, typically a freeway or arterial, that permits traffic to avoid part or all of an urban area.



Candlestick barriers
Plastic poles used to channel traffic. Normally used in long-term traffic control in lieu of orange drums in tight construction areas.

Cement Recycled Asphalt Base Stabilization (CRABS)
This is a resurfacing process that involves grinding the existing roadway surface down to the gravel base, then adding a strengthening agent, such as cement, to the old asphalt. The mixture is then compacted and used as the base for a new layer of asphalt. The section is then overlaid with a new layer of pavement.

Child safety seat
Idaho law requires that every child riding in a car who is younger than 4 and weighing less than 40 pounds must be in a safety seat. Children who have outgrown child safety seats should be in a booster seat. More

Class 1 road
Hard surface highways including interstates and U.S. numbered highways (including alternates), primary state routes and all controlled access highways.

Class 2 road
Hard surface highways including secondary state routes, primary county routes and other highways that connect principle cities and towns, and link these places with the primary highway system.

Class 3 road
Hard surface roads not included in a higher class and improved, loose surface roads passable in all kinds of weather. These roads are adjunct to the primary and secondary highway systems. Also included are important private roads such as main logging or industrial roads that serve as connecting links to the regular road network.

Class 4 road
Unimproved roads that are generally passable only in fair weather and used mostly for local traffic. Also included are driveways, regardless of construction.

Class 5 road
Unimproved roads passable only with 4-wheel drive vehicles.

Congestion Mitigation Air Quality Program (CMAQ)
A funding category under the Transportation Equity Act for the 21 st century (TEA-21) transportation bill. The funding is generally used for air quality projects.

Cold in-place recycling
Crews break up a layer of old pavement, add asphalt, shape it and use it as the base for a top layer of new pavement. This process is used on medium or low-volume roads.

In rural areas, routes serving intra-county, rather than statewide travel. In urban areas, streets providing direct access to neighborhoods as well as direct access to arterials.

Community Planning Association of Southwest Idaho (COMPASS)
A non-profit association created by local governments. Provides a forum to address and prioritize region-wide issues; serves as a catalyst to ensure local government involvement in building region-wide consensus, develops and supports policies to achieve region-wide solutions. More

A broad geographical band that follows a general directional flow connecting major sources of trips that may contain a number of streets, highways and transit route alignments.

Corridor analysis
A detailed analysis of a roadway performed for the purpose of obtaining the most accurate projected traffic volumes. The analysis takes into account existing traffic volumes, projected growth, and major traffic generating locations. A corridor analysis will yield projected traffic volumes for every movement allowed on a facility including main lane, ramp, frontage road, and turning volumes.

A drainage structure beneath an embankment. Culverts, as distinguished from bridges, are usually covered with embankment and are composed of structural material around the entire perimeter.

Curb weight
The weight of a motor vehicle with standard equipment, maximum capacity of fuel, oil, and coolant; and, if so equipped, air conditioning and additional weight of optional engine. Curb weight does not include the driver.

Disadvantaged Business Enterprise program (DBE)
Provides opportunities for small and minority-owned businesses to contract with the transportation department. More

Material applied to roadways to prevent ice build-up or to melt ice.

Divided highway
A highway with a median that separates lanes of traffic going opposite direction. Usually two lanes in both directions, usually high volume highways.

Dowel-bar retrofit
An innovation technique. Metal dowel bars inserted across adjacent concrete slabs joints in the pavement. The dowel bars distribute the weight of traffic across each joint evenly and keep the joints from moving up and down, which reduces damage to the roadway.

Draft Environmental Impact Statement (DEIS)
An environmental document that is prepared when it is initially determined that the action/project may cause significant impacts to the environment, when environmental studies and early coordination indicate significant impacts, or when review of the environmental assessment indicates that the impacts anticipated to result from the project may be significant. The DEIS compares all reasonable alternatives to the proposed project and summarizes the studies, reviews, consultations, and coordination required by legislation and Executive Orders to the extent appropriate at the draft stage in the environmental process. This document lists all entities from which comments are being requested.



Environmental assessment (EA)
Studies the project's impact on wildlife, wetlands, cultural resources, farmland, water and air quality and other environmental issues.

Environmental Impact Statement (EIS)
An analysis of the environmental impacts of proposed land development and transportation projects; conducted for federally funded or approved projects per NEPA. A draft EIS is circulated to the public and agencies with approval authority for comment.

Environmental Protection Agency (EPA)
A Federal agency charged with protecting the natural resources on the nation. More

Feasibility Study
A study about a project's feasibility. The study addresses issues including the project's benefits, costs, effectiveness, alternatives considered, analysis of alternative selection, environmental effects, public opinions, and other factors.

Federal Aviation Administration (FAA)
The FAA oversees the safety of civil aviation. Its safety mission is first and foremost and includes the issuance and enforcement of regulations and standards related to the manufacture, operation, certification and maintenance of aircraft. The agency is responsible for the rating and certification of airmen and for certification of airports serving air carriers. It also regulates a program to protect the security of civil aviation, and enforces regulations under the Hazardous Materials Transportation Act for shipments by air. The FAA, which operates a network of airport towers, air route traffic control centers, and flight service stations, develops air traffic rules, allocates the use of airspace, and provides for the security control of air traffic to meet national defense requirements. More

Federal Highway Administration (FHWA)
The federal agency responsible for the administration of federal highway funds. FHWA coordinates highway transportation programs in cooperation with states and other partners to enhance the country's safety, economic vitality, quality of life, and the environment. Major program areas include the Federal-Aid Highway Program, which provides federal financial assistance to the States to construct and improve the National Highway System, urban and rural roads, and bridges. This program provides funds for general improvements and development of safe highways and roads. The Federal Lands Highway Program provides access to and within national forests, national parks, Indian reservations and other public lands by preparing plans and contracts, supervising construction facilities, and conducting bridge inspections and surveys. More

One who uses traffic control signs to manually direct traffic.

Fog coat
Light finish oil spray applied over seal coats to keep chips in place. Normally used in high traffic/speed areas.

Frontage road
A road that parallels a larger highway and provides access to communities, stores, etc. Frontage/service roads limit the number of entrance and exit points onto a major roadway, reducing conflicts and improving safety.

Fuel tax
Idaho 's fuel tax is 25 cents per gallon. The per gallon Federal Motor Fuel Excise Tax is 18.4 cents on gasoline, 13.6 cents on LPG, 24.4 cents on diesel fuel, 13.0 cents on gasohol, 19.4 cents on aviation gas, and 4.4 cents on jet fuel. These monies go to the Federal Highway Trust Fund.

Generic term for material used in several different roadway applications.

Beams made of steel or concrete that are mounted on top of the bridge's foundation and help support the road.

Geographic Information System (GIS)
A system of information, organized in layers that can be applied to a specific georgraphic location to such things as population density, traffic volume, business development, etc.

Global Positioning System (GPS)
A satellite-based radio navigation system that identifies specific locations on Earth relative to longitude and latitude.

Method of smoothing road or side slope surfaces during construction.

High Occupancy Vehicle (HOV)
Vehicles having more than one occupant. Examples include carpools, vanpools, buses, and mini-buses. Transportation systems may encourage HOV use by having designated HOV lanes.

High Occupancy Vehicle (HOV) Lane
High Occupancy Vehicle Lane . Exclusive road or traffic lane limited to buses, vanpools, carpools, emergency vehicles, and in some cases, single occupant motorcycles. HOV lanes typically have higher operating speeds and lower traffic volumes than adjacent general purpose lanes. HOV lanes have proven to be successful in major metropolitan areas across the US ; however, their full effectiveness is usually not realized until about one to two years after implementation.

Hot in-place recycling
Crews heat up and grind off the top few inches of pavement, which is thoroughly mixed with new material and put back down. This process, chiefly used on high-volume roads, creates a road bed that closely resembles a new road in consistency and strength.



Idaho Traffic Safety Commission
Reviews traffic safety issues, promotes local and state cooperation, recommends programs for federal aid and supports motor vehicle crash prevention.

Impaired driver
A driver whose judgment is impaired by alcohol or drugs.

Partial pavement removal and replacement, normally used to eliminate ruts in roadway surface.

Intelligent Transportation Systems (ITS)
ITS uses electronics to monitor traffic and communicate with motorists. Examples include variable message signs and video traffic cameras.

Interagency Working Group (IWG) for Public Transportation
IWG's mission is to provide leadership in coordinating safe, efficient and accessible public transportation services to Idaho .

Intermodal transportation
Transportation that involves the interchange between transportation modes, such as automobiles, mass transit such as buses and railway. Intermodal transportation enables people and goods to be consolidated into larger groups that can be transported at lower costs. In addition to reducing costs, it enables greater logistic flexibility than can also reduce congestion and travel time.

Jersey barriers
Preformed concrete dividers that separate traffic or are used in place of guardrails on some routes.



Local highway technical assistance council (LHTAC)
LHTAC assists local highway jurisdictions (cities, counties and highway districts) with using available resources for maintenance and construction in the most efficient and effective manner possible. LHTAC makes recommendations to the Idaho Transportation Board for the distribution and prioritization of federal funds for local highway projects and assists the Legislature by providing research and data. More

Metric unit for .62 miles.



Magnesium chloride
A liquid that is sprayed on roads and works like anti-freeze by lowering the freezing temperature of water, preventing ice from forming a strong bond to the road.

The area that divides traffic moving in opposite directions on a single roadway.

Metropolitan Planning Organization (MPO)
An association of local agencies established for mutual benefit and to help coordinate planning and development activities within a metropolitan region. Establishment of the MPO is required by law in urban areas of over 50,000 population if federal funds are to be used. The MPO consists of two groups.
1. The Policy board is comprised of officials representing the counties, cities, and state agency.
2. The technical advisory group consists of professional planners and engineers who are usually employees of the same agencies.
The MPO is not a level of government. However, the MPO has "effective control" over transportation improvements within the area since a project must be a part of the MPO's adopted plan in order to receive federal funding.

An overlay technique in which a machine mixes the oil and chips and then drops the mixture onto the road together. The mixture is used to fix ruts and as a surface treatment. Result offers skid-resistance for motorists.

Motor Carrier Advisory Committee
Reviews regulations, statutes and general issues relating to motor carriers and advises the transportation department and staff.
National Environmental Policy Act (NEPA)
The National Environmental Policy Act requires federal agencies to integrate environmental values into their decision-making processes by considering the environmental impacts of their proposed actions and reasonable alternatives to those actions.

National Traffic Safety Administration (NHTSA)
Under the U.S. Department of Transportation, NHTSA is responsible for reducing deaths, injuries and economic losses resulting from motor vehicle crashes. NHTSA investigates safety defects in motor vehicles, sets and enforces fuel economy standards, helps states and local communities reduce the threat of drunk drivers, promotes the use of safety belts, child safety seats and air bags, investigates odometer fraud, establishes and enforces vehicle anti-theft regulations and provides consumer information on motor vehicle safety topics. More

National Transportation Safety Board (NTSB)
NTSB is an independent Federal agency charged by Congress with investigating every civil aviation accident in the United States and significant accidents in the other modes of transportation -- railroad, highway, marine and pipeline -- and issuing safety recommendations aimed at preventing future accidents. More



A new layer of pavement placed on a road's surface. During the process, hot oil is sprayed on the road, then chips are applied on top of it to seal the road. Generally applied to full width of existing roadway surface, to provide smoother riding surface.

Concrete rails on a bridge.

Person trip
A trip by one or more persons in any mode of transportation. Each person is considered as making one person trip. For example, four persons traveling together in one auto make four person trips.

Pilot car
A car specifically marked to lead traffic through a construction or work zone.

Port of Entry (POE)
Idaho has six permanent Ports of Entry that ensure compliance of commercial carriers to Idaho laws and restrictions and provide information about Idaho . The Ports of Entry are: East Boise , Cotterel (Rupert), Hollister ( Twin Falls ), Huetter (Coeur d'Alene), Inkom and Lewiston . A “roving” Port of Entry also serves commercial carriers at various locations throughout the state.

Public Transportation Advisory Council (PTAC)
The council is made up of one member from each of Idaho 's six districts and advises the Idaho Transportation Department on issues and policies regarding public transportation.

Punch list
A task list kept by an engineer to ensure that all jobs are completed on a project. Similar to a check list.



Metal rod reinforcement for concrete roadway and structures.

In highway construction, the graded portion of a highway within top and side slopes, prepared as a foundation for the pavement structure and shoulder.

A process that removes the top few inches of asphalt in preparation for a new asphalt surface.

Rumble strips
A series of grooves cut perpendicular into the shoulder of the pavement. When a vehicle drifts over the rumble strips, a loud noise and vibration results, serving as a warning to drivers.

Runaway truck ramp
A short inclined roadway constructed of sand or other unconsolidated material that exits gradually from and generally runs adjacent and uphill to the right lane of a descending highway, expressly for the purpose of stopping runaway trucks.

Road Weather Information Systems (RWIS)
Provides real-time atmospheric weather data, pavement temperature and surface conditions. As part of ITD's Road Report, the RWIS site features web cam photos from 15 locations in Idaho , plus sites in Montana , Oregon , Utah , Washington and Wyoming . Links to weather forecasts, weather warnings, and radar and satellite images also are available. More

Sanderson Index
System developed by ITD's Gary Anderson that defines the relative congestion of a specific road/highway; comparing ideal drive times (minimal or no traffic) with congested drive times. Results are shown in decimal form, ie. 2.2.

Scenic Byway Advisory Committee
A 15-member committee that advises the transportation board about scenic byway issues, including scenic byway eligibility, establishment and support.

Scoping process
An initial step in the preconstruction process in which public meetings are held to determine opinions about a potential project. It is one of the standards of the National Environmental Policy Act, a process that collects public input, technical assessment and evaluation to determine the best alternative for a particular project.

Scrub coat
Crews apply a liquid asphalt and sand mixture to fill holes and ruts in a road's surface. This process is usually done prior to repaving a road.

Seal coat
A process of spraying liquid asphalt on the road surface followed by a layer of crushed rock. A seal coat protects the existing road against water damage, adds traction to the road surface and prolongs its life.

Seat belt
Idaho law mandates that everyone in a motor vehicle must use a seat belt at all times when the vehicle is in motion.

Strategic Highway Research Program (SHRP)
Seven technology areas encompass the products of the SHRP, including: anti-icing/Road Weather Information Systems (RWIS), concrete assessment and rehabilitation, high performance concrete, innovative pavement maintenance materials, pavement preservation and more.

Slurry seal
Asphalt mixed with fine aggregate to extend pavement life. Generally used in urban areas. Also levels road surface. Serves the same purpose as a seal coat but it will fill in ruts.
Speed limit
Determined by the transportation bard upon recommendations from staff or local jurisdictions. Generally 75 mph on interstates (unless near a metropolitan area or otherwise posted) and 65 or 55 on U.S. and state highways.
State Transportation Improvement Program (STIP)
The department's 5-year plan for all modes of transportation. More



Transportation Equity Act for the 21 st Century (TEA-21)
A federal funding bill for transportation (except Aeronautics); expired Sept. 30, 2003 .

Transportation Research Board (TRB)
Serves as an independent adviser to the federal government and others on scientific and technical questions of national importance. Promotes innovation and progress in transportation through research; stimulates research and offers research management services that promote technical excellence; provides advice on policy and programs. More

The Road Information Project (TRIP)
A nonprofit organization that promotes transportation policies that relieve traffic congestion, improve air quality, make highway travel safer and enhance economic productivity. More

Vehicle Investment Program (VIP)
The program uses special funds approved by the Idaho Legislature to purchase public transportation vehicles. Funds are combined with federal and local resources.

Variable message sign
Computer-controlled highway information signs – either permanent or movable – that warn of traffic restrictions or hazards.



Vehicle Mile of Travel (VMT)
A unit to measure vehicle travel made by a private vehicle, such as an automobile, van, pickup truck, or motorcycle. Each mile traveled is counted as one vehicle mile regardless of the number of persons in the vehicle.