Resources & Links

This page will expand to provide you with access to the studies and documents prepared for the C-470 Corridor project.

Glossary of Definitions


Portions of this glossary can also be found in the Federal Highway Administration book, A Guide for HOT Lane Development.

Automatic Vehicle Identification (AVI): A technology system using transponders on vehicles and outside sensors to determine if vehicles on toll lanes are carrying a valid transponder and what the vehicle's classification is (truck vs. passenger car, SOV vs. HOV). This system also processes the appropriate toll transaction based on the information.

Auxiliary Lanes: Acceleration lanes and deceleration lanes and other lanes associated with providing better access to and from interchanges.

Benefit-Cost Ratio (BCR): The ratio of a project's present value benefits to its present value costs. The BCR is useful for comparing projects of different scale or financial size since it assesses economic efficiency.

Bicycles/Pedestrian lanes: Shared use lanes connecting residential, retail, office and open lands for alternative transportation usage.

Bus Rapid Transit (BRT): Could operate in a fixed guideway physically separated from traffic, dedicated right of way, Express lanes or HOV lanes.

Bus: Operates in general purpose travel lanes, express lanes or HOV lanes.

Categorical Exclusion (CatX): A NEPA document prepared for certain actions that are known through past experience to have no significant environmental impact and therefore "excluded" from future NEPA processing.

Closed Circuit Television (CCTV): A video monitoring and security system used to provide continuous traffic monitoring by the facility operator along the length of the facility and particularly at points of entry and tolling locations.

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Denver Regional Council of Governments (DRCOG): The Denver regional planning agency for transportation projects. The Metropolitan Planning Organization (MPO) for the major metropolitan area of Denver.

Detector Loops (Loop Detector Amplifiers): An AVC system component imbedded in the pavement and used to detect and classify the types of vehicles crossing over them. The loops are linked to the lane controller and can be used individually to count traffic or to trigger the violation enforcement cameras or in tandem to measure vehicle speeds.

Differential Pricing (Variable Pricing): Time-of-day pricing and tolls that vary by other factors like facility location, season, day-of-week, or air quality impact.

Dynamic Pricing: Tolls that vary in real time in response to changing congestion levels, as opposed to variable pricing that tolls on a fixed schedule.

Economic Rate of Return (ERR): The economic rate of return (ERR), sometimes referred to as the internal rate of return, gives the effective discount rate for which the project's benefits would just equal its costs, in present value terms. In other words, it is the discount rate that yields a BCR of 1.0.

Electronic Toll Collection (ETC): Systems deploying various communications and electronic technologies to support the automated collection of payment at toll booths and other collection points. Collectively, the application of these technologies increase system throughput, improve customer service, enhance safety, and reduce environmental impacts.

Environmental Assessment (EA): An EA is a concise document summarizing technical analysis to support the discussion of alternatives and their associated impacts. If there are no significant impacts, a Finding Of No Significant Impact (FONSI) is prepared. The FONSI completes the NEPA process.

Environmental Impact Statement (EIS): An evaluation of all reasonable alternatives that discusses why other alternatives were eliminated from the detailed study. The EIS also describes mitigation measures that are required to be incorporated into the implementation of the preferred alternative. The EIS is only conducted if the anticipated impacts of the federal action are found to be significant. A Record of Decision (ROD) is prepared as the final decision of the preferred alternative in the EIS.

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Existing Conditions: Current conditions and trends that include physical, environmental, cultural and social features. Basically, what is out there today.

Express Lanes (EL): A lane or set of lanes physically separated from the general-purpose capacity provided within major roadway corridors. Express lane access is managed by limiting the number entranced and exit points to the facility. Express lanes may be operated as reversible flow facilities or bi-directional facilities.

Express Service: Point to point bus service, often from a residential area directly to an employment center.

ExpressToll Lanes (ETL): Managed express lanes that every vehicle traveling on must pay a toll.

E-Z Pass: An electronic toll collection technology deployed by a regional consortium of transportation agencies in Delaware, New Jersey and New York. The technology is compatible with similar systems used by tolling agencies in several northeastern states. Plans call for the deployment of E-Z Pass on more than 700 toll lanes along 415 miles of roads, tunnels and bridges in the Northeast United States.

Fees for Entering: These are 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.

Fixed Pricing: Tolls that remain the same throughout time; usually based on distance.

Finding of No Significant Impact (FONSI): A FONSI is the decision document which completes the EA process.

General Purpose Lanes: Traffic lanes available for use by the general public without any restrictions or tolls.

High-Occupancy Toll Lanes (HOT lanes): Managed, limited-access, and normally barrier-separated highway lanes that provide free or reduced-cost access to HOVs and also make excess capacity available to other vehicles not meeting occupancy requirements at a market price.

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 vanpools, as well as buses.

HOV Lane: An exclusive traffic lane limited to carrying HOVs and certain other qualified vehicles.

Inherently Low Emission Vehicles (ILEV): Alternative fuel, clean air vehicles. Certain states (e.g. California) have authorized the use of ILEVs in HOV lanes regardless of occupancy (Assembly Bill 71). Related terms include Zero-Emission vehicles (ZEVs), Ultra-Low-Emission (ULEV), and Super-Ultra-Low-Emission (SULEV) vehicles powered by alternative fuels.

Incident Management: Managing forms of nonrecurring congestion, such as spills, collisions, immobile vehicles, or any other impediment to smooth, continuous flow of traffic on freeways.

Infrared Light Curtains: An ETC system component installed in pairs to sense the separation between two vehicles passing through a lane, as well as height depending on the number of beams deployed. The information passed on to the lane controller is used in conjunction with the loop detectors to support the correct grouping of axles and to identify large trucks or vehicles pulling trailers.

Intelligent Transportation Systems (ITS): A broad range of diverse technologies such as information processing, communications, control, and electronics which can help transportation systems in many ways, including congestion management.

Interoperability: The ability to provide of reciprocal privileges for users of electronic toll collection systems on other facilities equipped with ETC systems.

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Lane Controller: A microprocessor ETC component that coordinates the activities of all equipment in a single lane and generates the transactions assigned to individual customers using that lane.

Lane Management Tools:

  • Access - Limiting or metering vehicle ingress to the lane or spacing access so that demand cannot overwhelm HOT lane capacity. See also Limited Access.
  • Eligibility - Limiting lane use to specific types of users, such as HOVs motorcycles, low emission vehicles, or trucks. For most typical HOT lane settings, eligibility requirements would be used during selected hours or at specific access ramps.
  • Pricing - Imposing a user fee on a lane that helps regulate demand by time of day or day of week. The fee increases during periods of highest demand.

Level-of-Service (LOS): Also known as "Traffic Service," LOS is a qualitative measure describing operational conditions within a traffic stream. LOS is based on service measures such as speed and travel time, freedom to maneuver, traffic interruptions, comfort and convenience. LOS is also affected by conditions such as number of access points, lane width, number of lanes, and percentage of large vehicles. Six levels of service are defined by letter designations from A to F, with LOS A representing the best operating conditions, and LOS F the worst.

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. Access may be restricted by 1) meeting signals, or 2) limiting the number of entrances and exits. Some restricted access lanes include HOV priority.

Light Rail Transit (LRT): Operates in a fixed guideway, physically separated from traffic.

Local Service: Local bus service, often provides service to a regional transit service station.

Managed Lane: A managed lane or lanes are designed and operated to achieve stated goals by managing access via user group, pricing, or other criteria. A managed lane facility typically provides improved travel conditions to eligible users.

Metropolitan Planning Organization (MPO): Federally mandated regional organizations responsible for comprehensive transportation planning and programming for in urbanized areas. Work products include the Transportation Plan, the Transportation Improvement Program, and the Unified Planning Work Program.

Mileage-Based Fee: A vehicular toll based on the vehicle miles traveled (VMT) in the jurisdiction.

Mixed-Flow: Combined flow of HOV vehicles and SOV vehicles.

Mobility Enhancement: Features or facilities that aid in moving people or goods. Mobility enhancements are often implemented in conjunction with capacity improvements.

Motor Vehicle Fuel Tax: Federal and state taxes levied on gasoline and other fuels.

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National Environmental Policy Act (NEPA): A national policy set for the protection of the natural environment and human health and welfare by promoting efforts to prevent or eliminate damage to the environment. From a transportation perspective, NEPA requires that alternatives be evaluated and decisions be made in the public's best interest based on a balanced consideration of the need for safe and efficient transportation.

No Action: An alternative that is used as the basis to measure the impacts and benefits of the preferred alternative(s) in an Environmental Assessment or other NEPA action. It consists of the existing conditions on the roadway, plus any safety or maintenance improvements which have been identified in the CDOT 5-Year Transportation Improvement Program.

Open Road Tolling: Fully automated electronic tolling in an open road environment allowing vehicles to travel at normal speeds when passing though toll collection points.

Price Elasticity of Demand: A measure of the sensitivity of demand for a commodity to a change in its price. It equals the percentage change in consumption of the commodity that results from one-percent change in its price. The greater the elasticity, the more price-sensitive the demand for the commodity.

Queue Jump: Elevated ramps or at-grade lanes that can be used by motorists stopped in traffic to bypass congestion.

Record of Decision (ROD): The decision document in an Environmental Impact Statement (EIS).

Reversible Flow: Lanes that can be operated in reverse direction to reduce congestion during certain peak periods.

Revenue Neutral: Revenue-neutral pricing strategies involve rebating some or all of the revenue generated by pricing to toll payers, where generating revenue is not an objective of value pricing.

Road Pricing: An umbrella phase 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.

Safety and Maintenance Improvements: Projects included in CDOT's 5-Year Transportation Improvement Program, completed regardless of a study's outcome.

Screening Criteria: Screening Criteria are used to compare alternatives. Often, there are two or three levels of screening that are needed, depending on the complexity of the project and the range of alternatives under consideration.

Single Occupant Vehicle (SOV): A vehicle occupied by only one person.

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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. Many sectors of the economy (telephone, electric utilities, and airlines) use such pricing to manage demand within the available capacity.

Toll Road: A road or section of road where motorists are charged a fee (or toll).

Toll Violation Camera: Fixed, short range, still cameras used to obtain single frame pictures which are deployed in individual lanes at tolling points. Toll violation cameras are aimed and focused to obtain images of the license plates of violating vehicles.

Transponder: 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 System Management (TSM): Strategies to improve the efficiency of the transportation system through operational improvements such as bus priority lanes, ramp metering, access management, Intelligent Transportation Systems, etc. TSM techniques improve system capacity without physical expansion or behavioral changes.

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Travel Demand Management (TDM): Strategies designed to make the most efficient use of existing transportation facilities by reducing the actual "demand" placed on these facilities. These strategies promote alternative modes, increase vehicle occupancy, reduce travel distances and ease peak-hour congestion. The TDM efforts can extend the useful life of transportation facilities and enhance mobility options.

Treadle: A pressure-sensitive device inserted in the pavement designed for directional counting of vehicle axles passing over them. These sensors are used as inputs to the lane controller to provide information on axle count and vehicle direction of travel, depending on the order in which are stripes are hit.

User Management: User management defines how and which types of users can utilize a facility, such as HOV occupancy requirements, access points, barrier separation, and user fees. Restrictions may vary by time of day or day of the week.

Value Pricing: Value pricing is a concept that uses monetary incentives to manage congestion during peak travel periods on tolled highways and crossing facilities.

Variable Message Signs (VMS): Electronic signage that employs ITS technology and centralized control systems to change messages in real-time, providing motorists with timely and useful information.

Variable Pricing: Fixed tolls that are based on time of day and used to manage congestion during peak travel periods.

Vehicle Hours Traveled (VHT): Total vehicle hours expanded traveling on the roadway network in a specified area during a specified time period.

Vehicle Miles Traveled (VMT): The measurement of the total miles traveled by all vehicles in a specified area during a specified time.

Vehicle Enforcement Systems (VES): Manual and computer systems used to enforce vehicle and motorist compliance with the usage guidelines for HOT lanes.

Vehicle Separators/Profilers: An AVI system component located on a gantry or at the side of a lane. They perform functions similar to light curtains. The class of vehicles is determined based on the profile of the passing vehicle.

Video Surveillance: The use of pan-tilt-zoom, steerable moving picture cameras to survey a toll plaza, ETC collection area, or a segment of roadway to monitor for incidents.

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Glossary of Acronyms


AASHTO American Association of State Highway and Transportation Officials
ACHP Advisory Council on Historic Preservation
ADT Average Daily Traffic
APE Area of Potential Effect
ASTM American Society of Testing and Materials
AST Above-ground Storage Tank
ATV All-Terrain Vehicle
AWDT Average Weekday Two-way Volumes

BA Biological Assessment
BDL Below Detection Limit
BFE Base Flood Elevation
BMP Best Management Practice
BP Before Present
BRT Bus Rapid Transit

CAA Clean Air Act
CAP Corrective Action Plan
CBD Central Business District. (generally downtown areas)
CDOT Colorado Department of Transportation
CDOW Colorado Division of Wildlife
CDPHE Colorado Department of Public Health and Environment
CEQ Council on Environmental Quality
CFR Code of Federal Regulations
CFS Cubic feet per second
CLOMR Conditional Letter of Map Revision
CMAQ Congestion Mitigation and Air Quality (Federal funds)
CNHP Colorado Natural Heritage Program
CO Carbon monoxide
CTE Colorado Tolling Enterprise
CWA Clean Water Act

dB(A) A-weighted Decibel
DIA Denver International Airport
DMNS Denver Museum of Nature and Science
DOT U.S. Department of Transportation
DRCOG Denver Regional Council of Governments

EA Environmental Assessment
EIS Environmental Impact Statement
EL Express Lanes
EO Executive Order
EPA U.S. Environmental Protection Agency
ESA Endangered Species Act
ESA Environmental Site Assessment
ETL ExpressToll Lanes

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FEMA Federal Emergency Management Agency
FHWA Federal Highway Administration
FIRM Flood Insurance Rate Map
FONSI Finding of No Significant Impact
FTA Federal Transit Administration

HABS/HAER Historical American Building Survey / Historical American
Engineering Record
HC Hydrocarbon
HOA Homeowner Association
HOT High-Occupancy Toll
HOV High-Occupancy Vehicle with more than one person.
HOV2+ High-Occupancy Vehicle with two or more persons.
HOV3+ High-Occupancy Vehicle with three or more persons.

ITS Intelligent Transportation System

Leq Equivalent Level (noise)
LOMR Letter of Map Revision
LOS Level of Service
LRT Light Rail Transit
LUST Leaking Underground Storage Tank

MFAA Mode Feasibility Alternatives Analysis
MIS Major Investment Study
MP Milepost
MPO Metropolitan Planning Organization
MS4 Municipal Separate Storm Sewer System
MSA Metropolitan Statistical Area
MSAT Mobile Source Air Toxins

NAAQS National Ambient Air Quality Standards
NAFTA North American Free Trade Agreement
NDIS Natural Diversity Information Source
NEPA National Environmental Policy Act
NHPA National Historic Preservation Act
NRHP National Register of Historic Places

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OAHP Office of Archaeology and Historic Preservation
OSHA Occupational Safety and Health Administration

Pb Lead
PM10 Particulate Matter less than 10 microns in diameter
P-n-R Park-n-Ride
PPI Public/Private Initiative

RAQC Regional Air Quality Council
RCRA Resource Conservation and Recovery Act
ROD Record of Decision
ROW Right of Way
RTD Regional Transportation District
RTP Regional Transportation Plan

SB 88 Senate Bill 88
SH State Highway
SHPO State Historic Preservation Office
SIP State Implementation Plan
SOV Single Occupant Vehicle
SRHP State Register of Historic Places
STIP Statewide Transportation Improvement Program
SWMP Storm Water Management Plan

TAZ Traffic Analysis Zone
TCLP Toxicity Characteristic Leaching Procedure
TDM Travel Demand Management
Transportation Equity Act for the 21st Century
TIP Transportation Improvement Plan
TOD Transit-oriented Development
TMO Transportation Management Organization
TSM Transportation System Management

UCM University of Colorado Museum
UDFCD Urban Drainage and Flood Control District
UP Union Pacific
USACE U.S. Army Corps of Engineers
USAFA U.S. Air Force Academy
USFWS U.S. Fish and Wildlife Service

VEL Value Express Lanes
Vehicle Miles Traveled
VPH Vehicles Per Hour

WPA Works Progress Administration

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Related Corridors

Counties & Municipalities