Glossary terms

Advanced Traffic Management System (ATMS)

remotely operated traffic management system for monitoring and managing operations of a freeway system including HOV lanes and arterial streets. Major elements of the system include surveillance, communications, and controls.

Automatic Vehicle Location (AVL)

the use of advanced technologies such as Global Positioning Systems (GPS) to monitor the location and movement of vehicles.

Average Daily Traffic (ADT)

a measure of traffic. The average number of vehicle trips generated over a specific time period.

Average Vehicle Occupancy (AVO)

the number of people divided by the number of vehicles (including buses) traveling past a specific point over a given time period.

Barrier Separated

an HOV lanei separated from the regular lanes of traffic by a concrete barrier. The facility may be one-lane/reversible or a two-lane bidirectional.

Benefit-Cost Ratio (B/C)

estimate of the anticipated dollars of discounted benefits achievable to a given outlay of discounted costs.

Bidirectional HOV Facility

preferential facility in which both directions of traffic flow are provided for.


a facility in which the HOV lanei is separated from the general-purpose lanesi by a designated buffer.

Bus Priority System

means by which transit is given preferential treatment or advantage over other traffic.

Bus Rapid Transit (BRT)

a term describing a bus operation that is generally characterized by operation on a separate right-of-way that permits high speeds.


a preferential roadway designed exclusively for use by buses.


Central Business District - commonly referred to as downtown.

Change of Mode

transfer from one type of transportation vehicle to another.

Commute Trips

trips that are taken on a daily or regular basis to work.

Concurrent Flow Lane

an HOV lanei that is operated in the same direction as the adjacent general-purpose lanesi.

Congestion Pricing

the policy of charging drivers a fee that varies with the level of traffic on a congested roadway. Congestion is designed to allocate roadway space, a scarce resource, in a more economically feasible manner. Synonym: congestion-relief tolling.

Continuous Access

an HOV lanei separated from the regular lanes of traffic by a painted stripe only.

Contraflow Lane

an HOV lanei operating in the opposite direction of the normal flow of traffic, designated for peak directioni travel.


resources used to produce a good or service.


segment of a trip made by a transit vehicle not in revenue service.


the increased travel timei experienced due to circumstances that impede a desirable movement of traffic.

Demand-Side Policies

policies aimed at reducing congestion by reducing the demand for travel either overall or by targeted modes.

Differential Pricing (Variable Pricing)

time-of-day pricingi and tolls that vary by other factors like facility location, season, day-of-week, or air quality impact.

Direct HOV/HOT Ramps

freeway entrance ramps set up as restricted use ramps for HOV/HOT facility-eligible vehicles.

Directional Split

the distribution of traffic flows on a two-way facility.

Dynamic Pricing

tolls that vary in response to changing congestion levels, as opposed to variable pricing that follows a fixed schedule.

Electronic Toll Collection

this refers to electronic systems that collect vehicle tolls, reducing or eliminating the need for tollbooths and for vehicles to stop.


function of maintaining the rules and regulations of a preferential treatment to maintain the integrity.

Enforcement Area

designated space on which enforcementi can be performed.

Environmental Assessment (EA)

study to determine the potential impacts on the environment from a project.

Environmental Impact Statement (EIS)

comprehensive study of all the potential impacts of a project funded with federal dollars.

Express Bus Service

bus service with a limited number of stops, usually at a high speed.

Fees for Entering

tolls charged to vehicles entering a particular facility or an area, but which do not depend on the distance traveled on the facility or in the area.


Federal Highway Administration.

Fixed Guideway

transportation system composed of vehicles that can operate only on their own guideways.

Freight Lane

a facility or lane restricted to authorized truck types.


Federal Transit Administration.

General-Purpose Lanes

lanes on a freeway or expressway that are open to all motor vehicles.

Grade Separation

the vertical separation of an intersecting transportation facility.

High Occupancy Vehicle (HOV)

a passenger vehicle carrying more than a specified minimum number of passengers, such as an automobile carrying more than one or more than two people. HOVs include carpools and vanpooli as well as buses.

High Occupancy Vehicle System

development and operation of a coordinated approach of physical improvements such as HOV lanes, park-and-ride lots, and supporting services and policies.

HOT Lanes (High Occupancy Toll Lanes)

HOV facilities that allow lower occupancy vehicles, such as solo drivers, to use these facilities in return for toll payments, which could vary by time-of-day or level of congestion.

HOV Lane

an exclusive traffic lane or facility limited to carrying high occupancy vehicles (HOVs) and certain other qualified vehicles.

HOV/HOT Freeway-to-Freeway Connectors

special freeway-to-freeway ramps restricted to HOV/HOT lane-eligible vehicles.

Incentive Programs

policies and techniques aimed at a specific behavior.


the provision of access into a roadway.

Inherently Low Emission Vehicles (ILEV)

alternative fueled clean air vehicles. Related terms include Zero-Emission vehicles (ZEVs), Ultra-Low-Emission (ULEV), and Super-Ultra-Low-Emission (SULEV) vehicles powered by alternative fuels.

Intelligent Transportation Systems (ITS)

the application of advanced technologies to enhance the operation and management of a transportation system.


the system of grade-separated ramps connecting two or more roadways.


facility connections between transportation modes.


privately owned vehicle operated on a fixed or semi-fixed schedule for a fare.


facility whereby transit riders are dropped off and picked up.

Level of Service (LOS)

qualitative measure that describes the operational conditions of a roadway or intersection.

Light Rail Transit (LRT)

modei of transit that operates on steel rails and is powered by overhead electrical wires.

Limited Access

access management used to restrict entry to a facility based upon facility congestion levels or operational condition, such as the presence of an accident or maintenance activities. Typically, access is not restricted by type of user.

Line Haul

portion of a commute trip that is nonstop between two points.

Local Bus Service

Bus routes and service characterized by frequent stops and slow operating speeds.

Main Lane

general-purpose lane on a freeway that is open to all motor vehicles.

Main-Lane Metering

regulating the flow of vehicles on general-purpose lanesi or on freeway-to-freeway connections through the use of traffic signals that allow vehicles to proceed at a predetermined rate.

Major Investment Study (MIS)

detailed study and assessment of the various options available for the purpose of selecting one for implementation.

Managed Lane

a lane or lanes that increase freeway efficiency by packaging various operational and design actions. Lane management operations may be adjusted at any time to better match regional goals.

Mileage-Based Fee

the fee charged for using a vehicle based on the vehicle miles traveled (VMT)i in the jurisdiction.


means of travel.

Mode shift

the change from one means of travel to another.

Motor Vehicle Fuel Tax

pricing of gasoline and other fuels.


facilities serving more than one transportation modei.

National Environmental Policy Act (NEPA)

legislation enacted in 1969 that requires that federally funded projects conduct an EIS to evaluate potential impacts.

Non-Attainment Area

a geographic area in which the level of air pollution is higher than the level allowed by nationally accepted standards for one or more pollutants.

Off-Peak Direction

direction of lower demand during the peak commuting period.

On-Line Station

modei transfer facility located along an HOV lanei or a fixed guidewayi system.

Origin-Destination Study

analysis of the starting and ending points or zones of people or vehicles.

Park-and-Pool Lot

facility where individuals can park their private vehicles and join a carpool or vanpooli. This lot is not normally served by public transportation.

Park-and-Ride Lot

facility where individuals can park their private vehicles and access public transportation.

Parking Management

strategies aimed at making better use of available parking supply. Parking managementi strategies include preferential parkingi or pricei discounts for carpools and/or short-term parkers, and disincentives for those contributing more to congestion.

Parking Surcharges

users who park in congested areas during the most congested periods are charged fees higher than those normally associated with the facilities they use.

Peak Direction

direction of higher demand during a peak commuting time.

Peak Hour

the hour in which the maximum demand occurs on a facility.

Peak Period

period in which traffic levels rise from normal levels to maximum levels.

Preferential Parking

incentive to encourage ridesharing. Usually located closer to the destination.


the direct costs borne by users for consuming a good or service.

Price Elasticity of Demand

a measure of the sensitivity of demand for a commodity to a change in its pricei. It equals the percentage change in consumption of the commodity that results from a 1-percent change in its price. The greater the elasticity, the more price-sensitive the demand for the commodity.

Priority Lane

lane providing preferential treatment to HOVs.

Priority Lane Pricing

concept of using congestion pricingi on an HOV lanei.


a line of vehicles or persons.

Queue Bypass

an HOV facility that provides a bypass around a queuei of vehicles delayed at a ramp or mainline traffic meter or other bottleneck location.

Ramp Meter Bypass

preferential treatment at a ramp meter in which a lane is provided for the exclusive use of HOVs to bypass the queuei.

Ramp Metering

procedure used to reduce congestion by managing vehicle flow from local-access on-ramps. The entrance ramp is equipped with a traffic signal that allows vehicle to enter the freeway at predetermined intervals.

Revenue Neutral

revenue-neutral pricing strategies involve rebating some or all of the revenue generated by pricing to toll payers, where raising money is not an objective of congestion pricingi.

Reverse Commute

travel timei between work/school and home in the opposite direction of the peak directioni of travel.

Reversible HOV Lane

facility in which the direction of traffic flow can be changed at different times of the day to match the peak directioni of travel.

Road Pricing

an umbrella phrase that covers all charges imposed on those who use roadways. The term includes such traditional revenue sources as fuel taxes and license fees as well as charges that vary with time of day, the specific road used, and vehicle size and weight.

Signal Preemption

an interruption of the normal operation of a signal in order to immediately serve a particular movement.

Signal Priority

technique of altering the sequence or timing of traffic signal phases using special detection in order to provide preferential treatment.

Special Use Lane

lane restricted for specific uses only.

Support Facility

a physical improvement that enhances HOV operations.


the volume of vehicle or passengers passing a specific point during a predetermined period of time.

Time-of-Day Pricing

facility tolls that vary by time-of-day in response to varying congestion levels. Typically, such tolls are higher during peak periods when the congestion is most severe.

Toll Road

a section of road where motorists are charged a use fee (or toll).

Traffic Assignment

the planning and modeling process of allocating trips by different modes and to different origins and destination and routes.

Traffic Assignment Zone

the division of a study area into subunits or zones allowing for a more detailed level of analysis.

Traffic Volume

the number of vehicles on a roadway.

Transit Center

modei transfer facility serving buses or other modes.


an electronic tag mounted on a license plate, built into a vehicle, or placed on the dashboard. The tag is read electronically by an electronic tolling device that automatically assesses the amount of the user fee.

Transportation Control Measure (TCM)

series of vehicle trip-reduction measures focusing on reducing travel by SOVs and increasing alternative modes.

Transportation System Management (TSM) - actions that improve the operation and coordination of transportation services and facilities.
Transportation/Travel Demand Management (TDM)

a variety of strategies, techniques, or incentives aimed at providing the most efficient and effective use of existing transportation services and facilities. Road pricingi is one category of TDM.

Travel Time

the length of time it takes to travel between two points.

Travel Time Reliability

term referring to the lack of variability in travel timei that can be expected using different facilities.

Travel Time Savings

time saved by using an HOV facility rather than the general-purpose lanesi.

Trip Generation Rates

number of vehicular trips to and from a development. These rates are used to identify the potential impacts of new projects.

User Management

which types of users can utilize a facility. HOV lanes are prime examples of user-managed facilities. Restrictions may vary by time of day or day of the week.

Value Pricing

a system of fees or tolls paid by drivers to gain access to dedicated roadway facilities providing a superior level of service compared to the competitive free facilities. Value pricingi permits anyone to access the managed lanes, and the value of the toll is used to ensure that the management goals of the facility are maintained.


prearranged ridesharing function in which groups of people travel together on a regular basis in a van.

Vehicle Miles Traveled (VMT)

the total distance traveled in miles by all motor vehicles of a specific group in a given area at a given time.

Violation Rate

number of vehicles that do not meet the minimum occupancy requirements of an HOV facility.

Volume to Capacity Ratio

the ratio of demand flow rates to capacity for a given type of transportation facility.