The following glossary represents terms that are frequently used during transportation studies.
Arterial streets provide high mobility with limited land access allowed. Intersections are spaced in 0.5 to 2 mile intervals in an attempt to increase mobility.
Average Daily Traffic (ADT)
The calculation of average traffic volumes in both directions of travel in a time period greater than one day and less than one year and divided by the number of days in that time period.
A process of evaluating the costs, benefits, and impacts of a range of transportation alternatives designed to address mobility problems and other locally-identified objectives in a defined transportation corridor, and for determining which particular investment strategy should be advanced for more focused study and development .
Bus is a mode of transit service characterized by roadway vehicles powered by diesel, gasoline, battery, or alternative fuel engines contained within the vehicle. Vehicles operate on streets and roadways in fixed-route or other regular service. Types of bus service include local service, where vehicles may stop every block or two along a route several miles long. When limited to a small geographic area or to short-distance trips, local service is often called circulator, feeder, neighborhood, trolley, or shuttle service.
Bus Rapid Transit (BRT)
Bus rapid transit (BRT) systems provide more effective and efficient bus service by using dedicated bus lanes, transit signal priority, and/or fewer stops on the route.
A study done to determine the quality of operation of a given intersection or roadway segment. The quality of operation is expressed in terms of a Level of Service (LOS).
Collector streets collect and distribute traffic between local streets and arterials by providing limited mobility in combination with land access. Intersections on collector streets are spaced at 0.5 mile intervals or less.
Complete Streets are designed, operated and maintained so they are safe, comfortable and convenient for all users – pedestrians, bicyclists, transit users and motorists of all ages and abilities.
The investigations of potential environmental impacts to determine the environmental process to be followed and to assist in the preparation of the environmental document.
Geographic Information System (GIS)
GIS combines hardware, software, and data. GIS organizes the data in many ways that can display patterns and trends.
Heavy Rail is a mode of transit service operating on an electric railway with the capacity for a heavy volume of traffic. It is characterized by high speed and rapid acceleration passenger rail cars operating singly or in multi-car trains on fixed rails; separate rights-of-way from which all other vehicular and foot traffic are excluded; sophisticated signaling, and high platform loading.
Light Rail Transit (LRT)
Light Rail is a mode of transit service (also called streetcar, tramway, or trolley) operating passenger rail cars singly (or in short, usually two-car or three-car, trains) on fixed rails in right-of-way that is often separated from other traffic for part or much of the way. Light rail vehicles are typically driven electrically with power being drawn from an overhead electric line via a trolley or a pantograph; driven by an operator on board the vehicle; and may have either high platform loading or low level boarding using steps.
Level of Service (LOS)
A qualitative concept which has been developed to characterize degrees of congestion as perceived by motorists. Letter designations, A through F, have been correlated to quantitative measures based on the amount of delay experienced along a corridor or an intersection. Level A represents the best conditions and level F the worst.
Local streets provide maximum land access and minimum mobility. Access to a local street is on an as needed basis to allow property owners access to a transportation facility.
Mitigation includes the following items: Avoiding the impact altogether by not taking a certain action or parts of an action; Minimizing impacts by limiting the degree or magnitude of the action and its implementation; Rectifying the impact of repairing, rehabilitating, or restoring the affected environment; Reducing or eliminating the impact over time by preservation and maintenance operations during the life of the action; Compensating for the impact by replacing or providing substitute resources or environments.
Activities identified in the environmental process intended to lessen the severity of any unavoidable environmental impacts precipitated by the proposed action.
Pertaining to or suitable for transportation involving more than one form of transportation, i.e. pedestrians, bicycles, vehicles, trucks, etc.
(also known as Active Transportation and Human Powered Transportation) includes walking and bicycling, and variants such as small-wheeled transport (skates, skateboards, push scooters and hand carts) and wheelchair travel.
The single hour in the day during which the maximum traffic volume occurs on a particular roadway. Peak hours are further classified as an A.M. peak hour, a P.M. peak hour, or a weekend peak hour.
Purpose of and Need for Action
The Purpose and Need identifies and describes the proposed action and the transportation problem which it is intended to address.
The capacity of a roadway is defined as the maximum hourly rate at which vehicles can reasonably be expected to travel through an intersection or section of roadway during a given time period. Some factors having a primary influence on the capacity of an intersection or roadway segment are: the number and width of lanes, other geometric considerations (sight distance, approach grades, turning radii), vehicle mix, turning percentages and signal timings.
Property owned by a government agency used for the construction of public facilities like a roadway or a bridge.
An early and open process for determining the scope of issues to be addressed in the environmental document and for identifying potentially significant issues related to the proposed action. Scoping is intended to focus the study effort on issues that are significant and avoid the collection of needless detailed information on insignificant issues.
A stakeholder is anyone who could be affected by the project and has a stake in its outcome.
A type of light rail transit service operating individual passenger rail cars on fixed rails along short distances, usually on streets in mixed traffic. Streetcar vehicles are typically driven electrically with power being drawn from an overhead electric line via a trolley or a pantograph; driven by an operator on board the vehicle; and may have either high platform loading or low level boarding using steps.
Traffic Control Device (TCD)
TCDs (signals, stop and yield signs) are devices to control the speed and movement of traffic.
Transportation System Management (TSM)
Transportation system management optimizes the performance of existing infrastructure by implementing projects designed to conserve capacity and improve safety and reliability.
Transit Signal Priority (TSP)
TSP makes transit service more efficient and effective by giving transit vehicles more green time and less red time at traffic signals.
The primary performance measure on interrupted flow facilities, especially at signalized intersections. For this element, average control delay is measured, which is expressed in seconds per vehicle. Control delay includes the time vehicles are slowing down approaching a traffic signal or stopped at the intersection.
Signs, maps and other graphic or audible methods to convey location and direction to travelers.