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Frequently Asked Questions | Glossary of Terms


Driving in Idaho

The 511 travel information service provides road and weather conditions, camera views, emergency closures and highway construction information 24-hours-a-day, seven-days-a-week.

By visiting or calling #511, travelers are updated as conditions change on Idaho’s highways.

Type of information available include:

  • Weather-related road conditions
  • Cameras & weather stations
  • Highway construction information
  • Emergency road closures
  • Traffic incidents & delays

For information about child safety seats, seat belts, highway safety grants and more, go to: ITD’s Highway Safety web page

“Quick Clearance” is the law in Idaho as of July 1, 2005. The legislation is designed to improve safety and traffic flow on the state’s interstates and major divided highways. If you are involved in a crash on one of these roadways that does not cause a death or injury, and you are able to safely drive your vehicle out of travel lanes, you are required to do so.

Why is this law important?

Some collisions occur as the result of another crash. In some cases, emergency responders are victims in these secondary crashes. Clearing the road following a crash and giving emergency responders plenty of room reduces the chance that another collision will occur.

For every minute a roadway lane is closed, it takes several minutes for traffic to recover. Closed travel lanes cause significant congestion and cost Idaho businesses and employees in missed work time, additional business expenses and increased fuel consumption.

What should I do if I am involved in a crash?

The law only applies to interstates and major divided highways. Signs along these roadways help clarify where the law applies. If you are on an interstate or major divided highway, move your vehicle to a shoulder, median or emergency lane if you can safely do so and the crash did not cause a death or injury. You should do this whether or not a law enforcement officer is on the scene. If an officer is present and directs you otherwise, always follow the officer’s instructions.

Will I be liable if I move my vehicle before the crash is investigated?

No one will be considered at fault for the cause of a collision, solely because they moved a vehicle in accordance with Idaho’s Quick Clearance Law.

How will this law impact law enforcement investigations?

The Quick Clearance Law will not interfere with any law enforcement officer’s duty to investigate crashes or enforce criminal, traffic or highway laws. However, it does give officers the authority to require removal of vehicles or debris from freeway travel lanes. The Idaho Transportation Department’s Incident Response crews assist law enforcement in clearing crash scenes along the busy Interstate in the Treasure Valley.

Idaho’s Quick clearance Law is sponsored by the Idaho Transportation Department and Idaho State Police.

Transportation in Your Local Community

Speed limits are intended to supplement the drivers’ judgment in determining what is a reasonable speed for particular road and weather conditions. Limits are imposed to assist Idaho law enforcement. They encourage better traffic flow by reducing the variances in speed.

Traffic limits that reflect the behavior of the majority of motorists are found to be the most successful. Laws that arbitrarily restrict the majority of drivers encourage wholesale violations, lack public support, and generally fail to produce desirable changes in driving behavior.

Establishing a speed limit in Idaho involves a three-pronged analysis:

  1. In accordance with federal guidelines, ITD uses the 85th percentile speed of free flowing traffic for determining a safe and reasonable speed. According to research, accident involvement is the lowest within that 85 percent. Speed limits are also determined by a combination of two investigations involving engineering and traffic.
  2. The engineering investigation involves determining the design of the road and its immediate environment. Engineers analyze such items as lane width, pavement type and condition of the road. They also look at terrain, parking conditions, residential development along the road and the number, width and types of entrances and intersecting streets.
  3. The traffic investigation involves gathering and analyzing traffic related data such as traffic volumes, accident frequency, and the effect of traffic control devices such as stoplights and stop signs.

After all variables have been considered and a speed limit is established, traffic should flow at a safe and efficient level.

  • ITD continually monitors speeds and crashes to determine correlations, and adjusts accordingly.

Does reducing a speed limit result in safer driving conditions?

Not necessarily. Reducing the limit below the warranted speed can actually be hazardous and unsafe. Studies have shown that merely reducing a speed limit has little effect on the speed at which motorists will travel. Furthermore, no published research findings have established any direct relationship between posted speed limits and accident frequency.

When determining speed limits, engineers attempt to set a realistic limit that the majority of drivers will obey and that can be reasonably enforced.

Stoplights are designed to ensure a safe and orderly flow of traffic. They provide safety for pedestrians and vehicles while crossing a busy intersection. Lights allow motorists to “take turns” when traveling through busy intersections and in the right locations. They can enhance both safety and efficiency for pedestrians and traffic.

In the wrong location, however, a stoplight can create numerous unnecessary hazards such as delays, congestion, and accidents.

The Idaho Transportation Department strives to find those locations where a light will help more than it will hinder. The purpose of stoplights is to relieve more congestion than they will cause. In every case, the safety of Idaho motorists is ITD’s primary consideration.

ITD works in conjunction with federal guidelines that establish minimum conditions under which a light installation can be considered. Traffic engineers assess whether or not a light is a proper means of traffic control by carefully assessing the intersection’s use by vehicles and pedestrians. The transportation department looks at the physical make-up of the intersection, roadside development and delays experienced by motorists during peak hours. ITD also considers average vehicle speed, the number and types of accidents that occur and future road construction plans.

What are the advantages of a stoplight?
Stoplights provide the maximum degree of control at intersections. They relay messages of both what to do and what not to do. Their primary function is to assign right-of-way to conflicting movements of traffic at an intersection. They do this by permitting conflicting streams of traffic to share the same intersections by means of time separation.

In some cases lights can contribute to safer driving conditions. This is most common at intersections where accidents involving vehicles approaching from different directions occur at an abnormally high frequency and other remedies to prevent these accidents prove unsatisfactory.

What are the disadvantages of a stoplight?
Stoplights in the wrong location can actually contribute to the problems they were meant to alleviate. Misplaced signals increase rear end accidents and in some cases, angle collisions still occur at signalized intersections when motorists run red lights.

Stoplights can also create unnecessary travel on alternate routes and a more congested traffic flow. They can also create excessive delays, which in turn increase driver aggravation and encourage motorists to disobey signals. This problem is increased when stoplights are placed too close to each other. On an average State Highway , where signals are placed one-half of a mile apart, a driver can maintain an average speed of 36 mph. When the signals are spaced one-quarter of a mile from each other, the maximum average speed a driver can maintain drops to 18 mph.

What are alternative solutions to a stoplight?
Many accidents at intersections are not caused by the absence of a stoplight: inattentive driving, drunk drivers, and speeding are common contributors. Other traffic control devices that might prove safer include turning lanes, warning signs, improved roadway lighting, and pedestrian crosswalks.

How do stoplights work?
There are two different types of stoplights in Idaho : fixed time and traffic response. Fixed time stoplights assign the green light to the different approaches of an intersection for a predetermined amount of time. Some can also be set to different lengths of green time during peak traffic hours. These types of signals are typically found in urban areas where traffic movement is fairly predictable.

Traffic responsive signals change the lights according to the amount of traffic in each direction. These signals use sensors to detect the amount of vehicles and automatically adjust the length of the green time. This allows as many vehicles as possible through the intersection before responding to the presence of vehicles approaching from another direction.

One of the Idaho Transportation Department´s (ITD) most important responsibilities is to ensure that the design of each state highway properly balances access and mobility. Access management is the tool used to provide this balance.

Roads serve two primary purposes; to provide mobility and access. Mobility is the efficient movement of people and goods. Access is getting those people and goods to specific properties. A roadway designed to maximize mobility typically does so in part by managing access to adjacent properties.

Most state highways serve a function somewhere between interstate highways, which have very limited access and high mobility, and local residential roads, which provide numerous accesses to properties but are not appropriate for long distance travel. Access Management Brochure

How does access management improve safety?
ITD access standards aim to provide the optimal balance between access and mobility by reducing points of traffic conflict. Conflict points are locations on a roadway where two vehicles can potentially cross paths. At a four-way intersection there are as many as 32 conflict points, each representing the location of a possible crash. Drivers can be overwhelmed by large amounts of conflict points, increasing the potential for accidents. Good access management strives to separate conflict points by providing a reasonable distance between driveways and median openings, and restricting certain movements at some median openings.

Poor access management compromises the safety and efficiency of the highway and can result in increased accidents, commute times, vehicle emissions and fuel consumption.

Will access management hurt my business?
ITD recognizes the time and money investment business owners put into establishing and growing their business. Both successful businesses and a safe and efficient highway system are crucial ingredients for the economic prosperity of our state.

The movements that occur at driveway locations can make it difficult for through traffic to flow smoothly at desired speeds when those driveways are too closely spaced. Through access management, traffic flow becomes efficient and congestion decreases, resulting in increased exposure to roadside businesses. This can also delay the need to widen a road for several years.

Even in situations where the implementation of access management creates a slightly longer route for customers to get to a business, national studies have found that customers have no problem driving a greater distance, including negotiating U-turns, to access a “destination” business (specialty retail stores, service-oriented businesses). In the case of “pass-by” businesses (gas stations, fast-food restaurants, etc.), studies have shown that as long as reasonable access is provided, access management modifications have little effect on their success.

Poor access management hurts businesses by creating congested, high accident roadways. Closely spaced and poorly designed driveways make it more difficult for customers to enter and exit businesses safely, and access to corner businesses may be blocked by backed up traffic. Newer businesses will seek out locations that have fewer access and congestion problems, and customers will patronize businesses with safer, more convenient access.

How can I be involved in developing my access future?
ITD encourages and seeks public input for roadway planning projects. Access management is always an important part of these discussions. Opportunities to give input for projects are publicized through the media, newspaper advertisements and direct mailings. We encourage you to get involved!

Anyone concerned with access management may also contact their ITD district office locations. Questions and comments are always welcome.

As part of the Highway Beautification Act, Federal Law requires the department to provide continuing, effective control of outdoor advertising. We do this by requiring signs placed within federally designated routes to meet size and placement criteria, which vary depending on the location of each sign. For more information on outdoor advertising requirements go to: ITD’s Outdoor Advertising web page.

Putting election posters on utility poles, trees, rocks or on temporary stakes within a highway right of way is prohibited. Election posters may be affixed to privately owned fences bordering the right of way, subject to local zoning ordinances, providing the owner grants permission and no portion of the poster protrudes onto public property. All unauthorized posters are subject to removal. The transportation department removes posters or signs when they obstruct a motorist’s view or are a distraction.

Maintaining and Building Idaho Roads and Bridges

Highways, aviation, rail and public transportation needs are considered when shaping Idaho’s transportation future. The transportation department recognizes and values the needs of a truly intermodal society, whether it involves improving at-grade railroad crossings, reconstructing freeway interchanges, repairing bridges, building bicycle and pedestrian paths, improving backcountry airstrips or resurfacing highways.

The department’s planning specialists work closely with state leaders, local governments, private commerce and individuals to ensure a responsive, efficient partnership.

How is the public involved?
Because Idaho’s transportation system belongs to the public, shared involvement in planning, developing and maintaining all facets of transportation is essential. That is the foundation upon which the transportation department’s public involvement program is based. Construction and maintenance programs reflect needs that emerge from the grassroots of Idaho. Public input is essential in locating interchanges, widening travel lanes, resurfacing roadways, determining traffic patterns and creating pedestrian and bicycle paths.

The public involvement process includes both talking and listening, teaching and learning. While projects are not expected to be unanimously endorsed by every citizen, the transportation department is committed to the two-way information exchange as an indispensable part of a representative decision- making process. These decisions balance the need for safe and efficient transportation with the need to preserve economic, social and environmental conditions. The transportation department strives to be not only a good provider, but a good neighbor as well. Project planning includes numerous opportunities for the public to convey needs and suggestions. Those lines of communication instill shared ownership and a common vision for Idaho’s transportation system. Information meetings and formal hearings provide public access to the process. By encouraging public involvement early and often in the planning and development of transportation projects, the department hopes to ensure a product that serves the best interests of the most people.

Who makes the decisions?
The seven-member Idaho Transportation Board meets monthly to receive input from the public and administrative staff members. The board establishes state transportation policy and guides the planning, development and management of a complex statewide transportation network. It is responsible for assuring Idahoans a safe and efficient system that enhances the economy and quality of life. To ensure widespread opportunities for public input, the board usually meets six times a year in Boise and once in each of the six districts.

The governor appoints transportation board members, who then are confirmed by the Idaho Senate. Six members represent and live in each of the administrative districts; the seventh member of the citizen board is selected by the governor to serve as chairman.

Six of the seven board members are appointed to six-year terms, beginning Jan. 31. Their terms are staggered, enabling one appointment each year. The seventh member, the chairman, serves at the pleasure of the governor, conducts the monthly meetings and votes on motions only in the event of a tie. No more than four members may be of the same political party.

The Idaho Transportation Department’s construction itinerary begins with the Statewide Transportation Improvement Program (STIP), a seven-year master plan. The STIP identifies projects that have been selected through an inclusive and ongoing process. It represents the vision of the department’s board and director, elected officials from throughout Idaho, user groups and concerned citizens, all of whom share in shaping the plan.

The STIP establishes schedules for a variety of projects, including:

  • Highway, bridge, bicycle and pedestrian facilities
  • Highway safety
  • Air quality
  • Railroad crossing safety
  • Airports
  • Public transportation
  • Transportation planning
  • A number of grant programs

Partnerships within the public and private sectors will continue to strengthen the department’s planning efforts. As the foundational tool for shaping future construction, the STIP also depends on public participation. Input is encouraged before the annual updated plan is presented to the transportation board for approval.

The Idaho Transportation Department or ITD is committed to providing high quality, cost-effective transportation systems that are safe, reliable and responsive for the economical and efficient movement of people and products.

Idaho’s transportation system is an integrated network of more than 60,000 miles of roads, about 4,000 bridges, 1,887 miles of rail lines, 125 public airports, and the Port of Lewiston. Of these, the transportation department has jurisdictional responsibility for almost 5,000 miles of highway (or nearly 12,000 lane miles), more than 1,700 bridges, and 30 recreational and emergency airstrips. Also included on the state highway system are 30 rest areas and 10 fixed ports of entry.

The transportation department also oversees federal grants to 15 rural and urban public transportation systems, provides state rail planning and rail-project development and supports bicycle and pedestrian projects. Inside ITD web page

How is ITD organized?
More than 1,600 employees statewide carry out the transportation department’s commitment to provide safe, efficient travel. They are located in virtually every part of Idaho, from headquarters in Boise to ports of entry at Idaho’s borders and maintenance buildings on rural highways.

Transportation Funding

Funding comes from federal, state and local taxes, and fees. Funding is driven by the department’s strategic plan, based on projected federal and state revenues and appropriations by the Idaho Legislature. The available revenues are allocated to six major areas: highways, motor vehicles, planning, aeronautics, public transportation and management support.

The major source of state funds for all road and street jurisdictions (state, county, highway district and city) is the Highway Distribution Account (HDA). Funds deposited into the account are collected from a number of sources and are distributed according to Idaho law. The funding sources for the highway distribution account are:

  • Gasoline and special fuel taxes: These taxes are collected by the Idaho Tax Commission and are deposited into the HDA. Idaho’s fuel tax is 32 cents a gallon. Similarly, taxes on special fuels, such as diesel and propane, also are deposited into the HDA.
  • Vehicle registrations: Another major source of revenue to the HDA is vehicle registrations. The registration fee for passenger cars is based on the age of the vehicle.
  • Truck registrations: Trucks weighing 8,000 to 60,000 pounds gross vehicle weight pay registration based on weight group and type of operation. Trucks with more than 60,000 pounds gross vehicle weight pay a single registration fee calculated by truck weight and mileage group. These funds also are deposited into the HDA.
  • Miscellaneous fees: Other HDA fees are derived from license plate fees (including personalized and specialty plates), driver licenses and fines. Combined, these fees represent a small percentage of the total account.

State highway account funds projects
Revenue from the HDA for the maintenance, repair and construction of Idaho’s 5,000-mile state system is deposited into the state highway account for transportation department use. The department receives approximately 56 percent of the HDA revenue after the deductions are made. The remaining amount is divided among city, county and highway district jurisdictions and the Idaho State Police. Revenue from sources such as permits and licenses is deposited directly into the state highway account for use by the transportation department. Those “other funds” represent approximately 10-12 percent of the total state revenue deposited into the state highway account.

Federal funds are critical
The other major funding source for Idaho highways is the Federal Highway Trust Fund. Those funds are authorized to Idaho for highway construction, planning, safety and other uses on a project-by-project basis.
Authorized funds are subject to caps and “holdbacks” at the federal level. Idaho is authorized to spend a percentage of its allocated funds every fiscal year. Major funding categories include: national highway system, surface transportation program, interstate maintenance, emergency relief, forest highways, bridges, congestion mitigation and air quality, and transportation enhancements.
Other sources provide funding to promote public safety campaigns, build recreational trails and improve scenic byways.

Gasoline and special fuel taxes are collected by the Idaho Tax Commission and are deposited into the Highway Distribution Account. Idaho’s fuel tax is 32 cents a gallon. Similarly, taxes on special fuels, such as diesel and propane, also are deposited into the Highway Distribution Account (HDA). The gas tax helps fund road and street jurisdictions, including all state, county, highway district and city jurisdictions.

If you have additional questions, please use the ITD “Contact Us” portal

Glossary of Terms

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. Learn more . . .

Aggressive driving Learn more . . .
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:

  • failing to yield right of way
  • passing a stop sign
  • speeding
  • driving too fast for conditions
  • tailgating
  • 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. Learn more . . .

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. Learn more . . .

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. Learn 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. Learn 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. Learn 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)
Funding to this program 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. Learn 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. Learn more . . .

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

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. Learn more . . .

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

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. Learn more . . .

Environmental Protection Agency (EPA)
A Federal agency charged with protecting the natural resources on the nation. Learn 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. Learn 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. Learn 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 32 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
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.

ITD stands for the Idaho Transportation Department. The ITD Headquarters is located in Boise, ID, and there are six district offices representing all the areas throughout Idaho. Learn more . . .

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. Learn more . . .

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. Learn more . . .

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.

Metric unit for .62 miles.

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. Learn more . . .

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.

  • The Policy board is comprised of officials representing the counties, cities, and state agency.
  • 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. Learn more . . .

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.

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. Learn 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. Learn 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. Learn more . . .

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. Learn more . . .

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 cameras from numerous locations in Idaho, plus links to sites in Montana, Oregon, Utah, Washington and Wyoming. Links to weather forecasts, weather warnings, plus radar and satellite images are also available. Learn 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.

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. Learn more . . .

SH stands for state highway or an Idaho route. SH 55 is also referred to as Idaho 55 or ID-55. The Idaho Transportation Department (ITD) takes care of interstates, U.S. routes and state highways (SH) in Idaho.

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
In rural areas, speed limits are generally 70 to 80 mph on interstates until nearing a metropolitan area or otherwise posted. On U.S. and state highways, speed limits range between 55 and 70 mph unless otherwise posted. Regional ITD staff determine the speed limit on highways. The Idaho Transportation Board gets involved with 80 mph speed limits on Interstate highways and 70 mph speed limits on other highways.

Speed limits cannot replace common sense, so the speed motorists drive on a slick and/or wet road may be much lower than the maximum posted speed allows. Learn more . . .

State Transportation Improvement Program (STIP)
The department’s seven-year plan for all modes of transportation. Learn more . . .

Transportation Asset Management Plan (TAMP)
Idaho’s Transportation Asset Management Plan is a tactical-level document which focuses its analysis, options development, programs, delivery mechanisms, and reporting mechanisms on ensuring that strategic objectives are achieved because it acts as a focal point for information about the assets, their management strategies, long-term expenditure forecasts, and business management processes. Learn more . . .

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. Learn 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. Learn 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.

If you have additional questions, please go to the ITD “Contact Us” portal