Minnesota Department of Transportation

511 Travel Info

Transportation Data and Analysis

Cartographic maps, GIS data, traffic monitoring programs, and LRS maintenance

traffic on a highway

Glossary

Acceptable Percent Change Criteria – We compare incoming adjusted short count data to the most recent official AADT at that location. If the percent difference falls within our acceptable threshold (Acceptable Percent Change Criteria), we use the incoming data to estimate AADT; otherwise, we request a recount.  For more details visit the Data Screening and Recounts section of the Collection Methods page.

Adjusted Count – raw traffic count that we adjust by the specific month and day-of-the-week Seasonal Adjustment Factor (SAF) from its assigned “cluster group”. If applicable, we may also use an axle correction factor (ACF).

Annual Average Daily Traffic (AADT) – the bi-directional estimate of total vehicles on a road segment on any given day of the year. This represents the total number of vehicles per year divided by 365 and is developed using factors to adjust for season, day of the week, and vehicle type.

Arterial Road – may be classified as major or minor; high volume urban road whose main function is to deliver traffic from collector roads to freeways and to/from urban centers.

Automatic Traffic Recorder (ATR) – permanent device in the pavement that automatically and continuously collects traffic data. 

Average Daily Load (ADL) - the estimate of a daily vehicle load on a roadway segment; calculated from the daily total vehicle type multiplied by their appropriate ESAL factors.

Average Daily Traffic (ADT) - a 24-hour traffic volume that should be qualified by a time period, (e.g., MADT – monthly average daily traffic; or ADT for the period 6/21/11-6/23/11)

Axle Correction Factor (ACF) - adjusts for vehicles with 3 or more axles that contribute additional axle hits to the raw 48 hour traffic count. These factors are calculated from vehicle classification counts and are only used on the Trunk Highway system.

Axle Load – the total weight transmitted by all wheels in a single, tandem (2), or tridem (3) axle configuration.

Base Year – in a traffic forecast, the year construction will be completed and the roadway will be open to traffic.

Bituminous type of paved asphalt road resembling or containing bitumen, typically black or near black in color.

Bituminous ESAL (BESAL) – the equivalent single axle load for a bituminous or flexible pavement.

Cartographic Representations – map features and symbols used for representation purposes and usually not to scale.

Cartography – the study and practice of making maps or representations of the Earth on a flat surface.

Cluster Group – set of ATR locations with similar traffic pattern characteristics; each group has a set of Seasonal Adjustment Factors (SAF) for each month of the year. These factors are applied to 48 hour short counts with a “middle day” of Tuesday, Wednesday, or Thursday.

Computer Aided Drafting/Design (CAD) – the GIM (Geographic Information and Mapping) Unit used Bentley Microstation CAD software to design roadways and create cartographic maps. GIM now integrates GIS to design, analyze and modify mapping products.

Concrete ESAL (CESAL) – the comparable single axle load for a concrete or rigid pavement.

Construction Project Log - index of all construction projects which are organized by county and control section, are available on the Data Products page. Information about trunk highways dates back to the first recorded work in the 1920s.

Continuous Counts – permanent sensors in the road pavement that report hourly counts during the year, through ATR/WIM and Wavetronix devices.

Control Section - state highway road system segment that is divided into shorter, more manageable parts for record keeping.

Coordinate System (Projection) - a system using numbers (coordinates) and axes (x, y, z) to represent points in a space of given dimensions. The GIM unit produced CAD maps using the projected State Plane coordinate system, and now produces GIS maps along with the OTSM office with the projected UTM Zone 15 N coordinate system.

Corporate/City Limits the defined boundary or border of a city.

Count Cycle – cycle lengths vary (counted every 1, 2, 4, 6, or 12 years) according to the type of roadway and location.  For more information visit the Traffic Counting Schedule section of the Collection Methods page.

County Maps – individual maps of Minnesota’s 87 counties showing all public roads and corresponding route systems outside municipal boundaries, as well as railroads, airports, city names and boundaries, political township names and boundaries, lakes, rivers, etc.

County Road (CR) - roads locally maintained by county highway departments in Minnesota; span a wide variety of road types, varying from minor arterials that carry large volumes of traffic to an improved road.

County State Aid Highway (CSAH) - county road dedicated as part of the state aid system. County State Aid routes receive authorized financial support from the County State Aid Highway Fund.

D factor – the traffic percentage moving in the peak travel direction during the 30th highest hourly volume of the year; calculated by dividing the higher directional volume occurring in the 30th highest hour by the total roadway volume for that hour.  

Data Screening – factoring incoming traffic counts and comparing the resulting adjusted (24 hour) count to the most recent official AADT for the same location. If the adjusted count falls within the “Acceptable Percent Change” criteria, it is determined valid, and this new data will help establish the official AADT calculation. If the adjusted count falls outside of the “Acceptable Percent Change” criteria, the count needs further examination. If a recount is necessary, it is assigned a priority based on the “Recount Decision Tree.”  For more details visit the Data Screening and Recounts section of the Collection Methods page.

Design Hour Volume (DHV) - the traffic for a selected hour of the day; usually the 30th highest hour of the year for Greater Minnesota and the peak hour for the Metro Area.

Design Lane Factor (DLF) - factor to estimate traffic volume and truck components on heaviest traveled lanes for assessing ESAL.

Directional Distribution (DD) or Directional Split - traffic direction split for a selected time period (usually the design hour) shown in “50/50” format, where the first number denotes north or east direction and the second number indicates south or west.

District – MnDOT divided Minnesota into eight operating districts based on geographic location and resources. For more information visit http://www.dot.state.mn.us/information/districts.html.

Divided Highways – adjacent roads with one or more lanes, carrying traffic in opposite directions and separated by a dividing strip made of sod, gravel, concrete, etc.

Draft AADT - traffic volume values that are currently estimated but not yet official.

Equivalent Single Axle Load (ESAL) factor – numeric factor based on the equivalent load concept representing the average effect each vehicle type has on the pavement. The equivalent load concept relates how axles in different configurations and weights affect pavement performance, compared to the effect of a single 18,000-pound axle. These ESAL factors can vary depending on commodities vehicles haul.

Federal Highway Administration (FHWA) http://www.fhwa.dot.gov/ – federal agency that administers federal funds and issues policy and procedure timetables to enact federal legislative directives. However, they do not have a direct role in creating urban transportation plans. The FHWA use OTSM’s continuous count data, annual AADT, and VMT estimates in federal-level travel analysis and allocating funds.

Functional Classification - collection of assorted road systems organized according to the type of service they provide. Functional class defines the role for how particular roads or streets aid traffic flow through a highway network. For more information, visit http://www.dot.state.mn.us/roadway/data/html/functional_class.html

Geographic Information & Mapping (GIM) – the section responsible for preparing and maintaining numerous cartographic products. Products include MnDOT's Minnesota Official State Highway Map, as well as individual maps for Minnesota's 87 counties, 854 cities, and over 1,700 townships.

Geographic Information Systems (GIS) - a system designed to capture, store, manipulate, analyze, manage, and present all types of geographical data.  The most common GIS software includes the ESRI brand ArcGIS family of applications.

Graded and Drained Earth Road – a road of natural earth, aligned and graded to permit reasonable motor vehicle use. Drained by longitudinal and transverse drainage systems.

Gravel (or Stone) Road - a road wearing surface consisting of gravel, broken stone, or other fragmented material; indicated on maps with the letter “E”.

Greater Minnesota Minnesota land outside the seven-county Metro Area.

Half Tolerance Guidelines – the ‘Half Tolerance Guidelines’ are half (inside) the Acceptable Percent Change Criteria or double (outside) the Acceptable Percent Change Criteria. When screening incoming short count data, or estimating AADT, the Half Tolerance Guidelines can help determine if a count should be reviewed more closely (outside half tolerance) or used for the official AADT (inside half tolerance). These guidelines support recount priority decisions. For more details visit the Data Screening and Recounts or AADT Estimation Procedures section of the Collection Methods page.

Heavy Commercial Annual Average Daily Traffic (HCAADT) – theoretical estimate of heavy commercial vehicles along a specific segment of roadway (both directions) on any day of the year. This estimate represents the total number of heavy commercial vehicles per year, divided by 365, and includes factors adjusting for seasons.

Heavy Commercial Average Daily Traffic (HCADT) – a 24-hour heavy commercial traffic volume, which is qualified by stating a time period (e.g., MHCADT – monthly average daily heavy commercial traffic, or HCADT for the period 6/21/2017-6/23/2017).

Heavy Commercial Traffic – traffic from all trucks with at least 2 axles and 6 tires.

Heavy Commercial Vehicle Miles Traveled (HCVMT) – derived from HCAADT (Heavy Commercial Annual Average Daily Traffic), and are important because the heavy vehicle volume on a road affects traffic operations, safety, and pavement performance.

Highway Performance Monitoring System (HPMS) http://www.fhwa.dot.gov/policyinformation/hpms.cfm – national level highway information system that includes data on the extent, condition, performance, use and operating characteristics of the nation's highways.  The OTSM office submits state-level traffic data to HPMS on a monthly and yearly basis.

Induction Loop – a coil of wire in the pavement that acts as an electrical circuit; when a vehicle passes over the loop, the inductance decreases and the detection device identifies the vehicle.

Intelligent Transportation Systems (ITS) data - encompasses a broad range of wireless and wire line communications-based information and electronics technologies. When integrated into vehicles and the transportation system's infrastructure, these technologies relieve congestion, improve safety, and enhance productivity.

K factor - the ratio of the 30th highest hour volume (combined directions) to the AADT, from continuous count location data.

Legend – the key to symbols used on a map; usually contains symbols with descriptions, as well as notes on projection, date, source, scale, units of distance, etc.

Legislative Route - a highway number defined by the Minnesota State Legislature. Routes 1 to 70 are constitutional routes and route numbers greater than 70 may be added or deleted by the legislature.

Local system roads - any road not on the Interstate or Trunk Highway system; can be designated as a CSAH (County State Aid Highway), CR (County Road), MSAS (Municipal State Aid Street), township, or municipal road.

Major Roads – general term describing higher-traffic roads. Depending on the map type, major roads may include Interstate, Trunk (US and State) Highways, and CSAH/County level roads.

Manual Count – a classification count taken manually for 4-16 straight hours. Collect data by hour and direction, and note body types.

Maximum Loaded Vehicle – heavy commercial vehicle type usually loaded to the legal gross weight limit (gravel trucks, grain trucks, tank trucks, etc). These body types in the traffic mix indicate the need to use ESAL factors higher than the default values.

Metro Area – the seven-county Twin Cities Metropolitan Area comprised of Anoka, Carver, Dakota, Hennepin, Ramsey, Scott, and Washington counties.

Metro Area Street Series – see Twin Cities Metro Area Street Series

Metro District – comprised of eight counties-- the seven-county Twin Cities Metropolitan Area plus Chisago County.

Metropolitan Planning Organization (MPO) - legal entities that coordinate the transportation planning process and lead the development of a metropolitan area's transportation plans. All urban areas over 50,000 in population must have an MPO if the agencies spend Federal funds on transportation improvements.

Microstation – a CAD software product developed by Bentley Systems that the GIM Unit uses to design roadways and create cartographic maps.

Mileage Chart – a Minnesota Official State Highway Map feature showing distances (in miles) between major cities.

Minor Roads – general term describing lower-traffic roads. Depending on the map type, minor roads usually include Municipal, MSAS, Township and Private roads.

MnESAL – Excel program that uses AADT/HCAADT and vehicle class data to forecast 20-year BESALs and 35-year CESALs. This information helps develop pavement design options.

Monthly Average Daily Traffic (MADT) – average daily traffic for a given month; calculated by traffic volume sums for all days in month, then dividing by number of days in month.

Municipal Boundary – see Corporate/City Limits

Municipal State Aid Street (MSAS) - municipal streets in cities above 5,000 in population, not already included on the state highway or CSAH (County State Aid Highway) systems. Municipal streets on the MSAS system are eligible for funding from the Municipal State Aid Highway Fund.

Municipality (City) Maps – maps of Minnesota’s 854 cities representing all public roads and corresponding route systems inside city boundaries, as well as railroads, airports, lakes, rivers, etc. Cities with populations over 5,000 usually have a higher scale proportion on individual maps than cities under 5,000.

National Highway System (NHS) - roadways important to the nation's economy, defense, and mobility; developed by the Department of Transportation (DOT) in cooperation with the states, local officials, and metropolitan planning organizations (MPOs).

No Public Maintenance Road – a primitive road not maintained for public travel, and barely passable by four-wheel vehicles.

Office of Transportation Systems Management (OTSM) – in MnDOT's Modal Planning & Program Management division that contains four units: Geographic Information & Mapping (GIM), Data Systems & Coordination, Traffic Forecasting & Analysis (TFA), and Weight Data & Engineering Coordination.

Paved Road – general term for a road with a firm and durable surface such as bituminous, concrete, or solid stone; sometimes indicated on maps with the letter “I”.

Peak (or highest) hour volume – the highest hourly traffic flow value in a 24-hour period. Higher traffic volumes occur during rush hour and rise to a peak in the evening. People returning from work are also driving for additional reasons at this time.

Piezos – sensors permanently installed in the pavement surface that collect volume, classification, and speed data. A digital signal is emitted when a vehicle passes over the sensor.

Private Road – a road or driveway located on privately-owned property for private use; has no public access, and is not maintained through public funds.

Projected Road – construction plans show a future road, designated by resolution. 

Raw Count – a non-adjusted traffic count.

Recount – if the adjusted volume exceeds the acceptable percent change margins and does not pass OTSM examination criteria, request an extra count. The “Recount Decision Tree” assigns a priority to all recounts. For more details visit the Data Screening and Recounts section of the "Collection Methods" page.

Reference Post or Reference Point - measure of the distance (in miles or meters) from a fixed position to the beginning of a highway segment. The location can be a state or county line or the point where the particular route originates.

Regional Development Organization (RDO) - involved in soliciting and evaluating projects and seek to integrate regional priorities in planning and project selection. Regional Development Organizations coordinate transportation with MnDOT following a work program framework. There are twelve RDO's in Minnesota. For more information, visit our Transportation Planning Partners page.

Regional Transportation Management Center (RTMC) http://www.dot.state.mn.us/rtmc/ – MnDOT facility in Roseville that provides the communications and computer infrastructure necessary for coordinated transportation management on metro freeways.  The RTMC is responsible for analyzing the effectiveness of traffic management tools, collecting traffic flow information, and developing new traveler information products.  Traffic data from the RTMC is used to estimate AADT at many locations.

Road Surface Types - “I” = Paved; “G” = Bituminous; “E” = Gravel

Scale – the ratio of a distance on the map corresponding to the distance on the actual ground. For example, the scale for most GIM-produced county maps is approximately 1:126,500 (1 inch = 2 miles).

Seasonal Adjustment Factors (SAF) – used to adjust incoming data to account for differences between weekday and weekend traffic, as well as monthly fluctuations in traffic volumes to determine AADT and HCAADT.

Sequence Number (SEQNUM) – unique number (e.g. 2465, 28637) to identify MnDOT traffic segments in the traffic monitoring program.

Soil-Surfaced Road – a natural soil road that is stabilized by mixed soil or an admixture.

State Aid – public funds used by the state government to partially support or improve eligible public local roads.

State Map – the Minnesota Official State Highway map; includes major roads and features covering the state of Minnesota and adjacent portions of Canada, North Dakota, South Dakota, Iowa, and Wisconsin.

Tractor Semi-Trailers (TST) - a large truck consisting of a towing engine and a semi-trailer that carries the freight. A semi-trailer does not trail completely behind the towing vehicle, but is attached at a point that is just forward of the rear-most axle of the towing unit.

Traffic Forecasting – the estimation of future traffic volumes and loads on a specific roadway segment.  Historic total volume, truck data, and potential socioeconomic changes help project effects on traffic segments.

Traffic Volume – count of motorized vehicles that travel past a certain location over a specific period of time.

Transportation Information System (TIS) – integrated database system that stores roadway related traffic information such as AADT and HCAADT, and roadway physical characteristics such as number of lanes, presence of medians, etc.

Travel Behavior Inventory (TBI) - surveys conducted by MetCouncil, MnDOT, and WisDOT that examines where, when, why, and how people travel.  Conducted about every ten years since 1949, the TBI is the most comprehensive source of travel data in the 19-county MN/WI extended metro region.

Travel Demand Modeling - forecasts the expected demand for transportation facilities using roadway, transit, land use, population, employment, and travel behavior data. The four steps in travel demand forecasting are trip generation, trip distribution, modal choice, and trip assignment.

Trunk Highway (TH) - major roadways such as Interstates, US Highways, and State Highways.

Trunk Highway Log Point File - ordered listing of landmarks such as intersections, railroad crossings, city limit boundaries, bridges, etc. that vehicles cross when driving along a trunk highway in the increasing (reference post) direction; available on the Data Products page.

True Mileage - number describing route reference post locations based on their accumulated (odometer) distance from the beginning of the route.

Twin Cities Metro Area Map – a single map covering the seven-county metro area.

Twin Cities Metro Area Street Series – a map series of 56 individual maps (including a reference grid map) covering the seven-county metro area and portions of the surrounding counties.

Tube Count - portable devices that span the width of a road to count axles and classify vehicles based on their axle spacing; generally taken for a period of 48 hours during weekdays and during the months of April-October.  District, county, city, and OTSM personnel to gather tube count data at more than 32,000 Minnesota locations over a four-year cycle.

20-year cumulative ESAL – forecast period to measure pavement damage for the design lane.

Typical Traffic – traffic volume that is typical for most of the time that the Annual Average Daily Traffic (AADT) estimate represents.  When scheduling traffic counts, we try to avoid effects due to construction, harvest, school vacations, or any other “unusual conditions.”  For more information visit the Construction Policy section of the Collection Methods page.

Unimproved Road – a basic, drivable, natural surface road.

Urban/Rural Status - the Census Bureau defines urban areas as developed areas that include residential, commercial, and other land uses; redefined after each decennial census. Rural areas cover all population, housing, and territory excluded from an urban area.

Vehicle Classification (VC) – categorization of traffic by 13 vehicle types (motorcycles, single unit trucks, semis with single or twin trailers, etc.); data is routinely collected on trunk highways and some local roads and used to produce HCAADT.

Vehicle Classification Scheme - the axle spacings of vehicles to classify traffic into 13 vehicle types.  View the Vehicle Classification Scheme table for more information.

Vehicle Classification Sites – trucks, buses, vans, motorcycles and cars, etc. are categorized at these locations.

Vehicle Miles Traveled (VMT) - measures the demand on our transportation network; computed by multiplying the AADT by the centerline road miles. Visit OTSM's Roadway Data page for annual figures.

Wavetronix – a radar device that classifies vehicle types by length, where it is impractical or unsafe to use tube counters.

Weigh-In-Motion (WIM) - permanent devices that continually collect and store vehicle data such as axle weight, axle spacing, length, speed, type, and count. WIM's emit an analog signal whose strength is directly proportional to the axle weight of the vehicle.