Traffic Monitoring Guide

Appendix A. GLOSSARY OF TERMS

Annual Average Daily Traffic (AADT) – The Annual Average Daily Traffic (AADT) identifies the average volume of traffic for a one day (24 hour period) during a data reporting year.

Annual Average Daily Truck Traffic (AADTT) – The Annual Average Daily Truck Traffic identifies the volume of truck traffic for a one day (24 hour period) during a data reporting year.

Annual Vehicle Distance Traveled (AVDT) – The annual vehicle distance traveled identifies the distance traveled by vehicles over a 1 year (365 day) period. The AVDT can be grouped according to functional classification of roads and/or vehicle classification strata.

ATR Site – The location of an automated traffic recorder (permanent station) used for collecting traffic volume data, now use the term CCS.

Axle Factor – Axle correction factors can be applied at either the point or system level. That is, axle correction factors can be developed either from specific vehicle classification counts at specific locations, or from a combination of vehicle classification counts averaged together to represent an entire system of roads.

Axle Weight – The weight placed on the road by all wheels of one axle (Oregon DOT).

Blank-Fill – When the value in a field does not consume all of the columns for the field, leading blanks are to be used starting at the left of the field. For example, if a field is five columns wide, and the data value is 250, then a blank-filled representation for this field is _ _ 250.

Continuous Count Station (CCS) – Volume counts derived from permanent counters (ATRs), for a period of 24-hours each day over 365 days for the data reporting year.

Coverage Count – Special temporary count taken on a 24-48 hour basis for a specific segment of road, usually associated with HPMS sections.

Daily Vehicle Miles Traveled (DVMT) - indicates how many vehicles have traveled over the distance of a route, for a data reporting year, when reported as an average day for a given year. (DVMT = AADT X section length)

Extent – Spatial coverage for which the data are to be reported: functional system, NHS, sample, paved etc.

Federal-Aid Highways – All NHS routes and other roads functionally classified as Interstate, Other Freeways and Expressways, Other Principal Arterials, Minor Arterials, Major Collectors, and Urban Minor Collectors.

FHWA – Federal Highway Administration.

Full Extent – A population comprised of all sections of a functional system of public roads, which serves as a statistical universe for HPMS sampling and census data collection.

Full Extent Data – Data that are collected in a census of a whole population, which for HPMS means data collected on all sections of a functional system of public roads.

Functional Systems – Functional systems result from the grouping of highways by the character of service they provide. The functional systems designated by the States in accordance with 23 CFR 470 are used in the HPMS.

Metadata – Describes how data are collected or converted for reporting; explains variations in data that do not warrant the establishment of a collection requirement (e.g., type of equipment used, sampling frequency etc.).

Monthly Average Daily Traffic (MADT) – For a CCS site that operates 365 days per year without failure, the MADT can be computed by adding the daily volumes during any given month and dividing by the number of days in the month.

National Highway System (NHS) – The National Highway System is a network of nationally significant highways approved by Congress in the National Highway System Designation Act of 1995 and redefined by MAP-21. It includes the Interstate System, other roads, and connectors to major intermodal terminals.

Sample Panel (HPMS) – A collection of designated roadway sections within a system of public roads that is stable over time and is used to estimate attributes for the entire system.

Seasonality Factor – Seasonal (or Monthly) factors are used to correct for seasonal bias in short duration counts.

Short Duration Count – Count taken on a 24-48 hour basis for roadway segment-specific locations. These counts may be used in special studies

Table of Potential Samples (TOPS) – A collection of roadway sections spanning the public road network that provides the sampling frame for selection of the HPMS Sample Panel.

Travel Monitoring Analysis System (TMAS) – the FHWA-provided online software used by States, MPOs and cities to submit data for Federal purposes.

User Profile and Access Control System (UPACS)– Federal Highway Administration’s access control for information systems. The UPACS has two major functions: it provides users with a menu of systems that they have access to and provides authorized personnel a mechanism for granting such access. The UPACS provides access control for FHWA’s applications through system-generated user IDs and user-supplied passwords and PINs, in combination with individual access profiles created for users by system owners.

Vehicle – Assembly of one or more units coupled for travel on a highway; vehicles include one powered unit and may include one or more unpowered full-trailer, or semi-trailer units.

Vehicle Axle – The axis oriented transversely to the nominal direction of vehicle motion, and extending the full width of the vehicle, that the wheel(s) at both ends rotate.

Vehicle Axle Spacing – For each vehicle axle, the horizontal distance between the center of that axle and that of the preceding axle; the axle spacing for the vehicle’s front axles is assumed to be zero.

Vehicle Class – The FHWA vehicle typology separates vehicles into categories, or classes, depending on whether they carry passengers or commodities. There are 13 vehicle classes identified by FHWA, as listed in Appendix C.

Vehicle Counts – The activity of measuring and recording traffic characteristics such as vehicle volume, classification, speed, weight, or a combination of these characteristics.

Vehicle Length – Overall length of a vehicle measured from the front bumper to the rear bumper.

Vehicle Miles Traveled (VMT) – Vehicle miles traveled indicates how many vehicles have traveled over the distance of a route, for a data reporting year, when reported as Annual VMT(VMT = DVMT x 365).

Vehicle Speed – Measure of how fast a vehicle is traveling in kilometers/hour or miles/hour.

Weigh In Motion (WIM) – A measure of the vertical forces applied by axles to sensors in the roadway. This is used to measure the weight carried by trucks to determine the appropriate depth for pavement sections.

Zero-Fill – When the value in a field does not consume all of the columns for the field, leading zeros are to be used starting at the left of the field. For example, if a field is five columns wide, and the data value is 250, then a zero-filled representation for this field is 00250.