Skip to contentUnited States Department of Transportation - Federal Highway Administration FHWA Home
Research Home
Report
This report is an archived publication and may contain dated technical, contact, and link information
Publication Number: FHWA-RD-98-057

Human Factors Design Guidelines for Advanced Traveler Information Systems (ATIS)and Commercial Vehicle Operations (CVO)

 

CHAPTER 12: GLOSSARY

Accuracy of routing information

 

Refers to the correctness, usually expressed as a percentage, of traffic information presented to motorists. In this context, accuracy is considered to be a binary concept; i.e., the information is either accurate or inaccurate. Although accuracy is most often discussed with respect to congestion levels associated with various routing options, it may also refer to total travel time estimates, estimates of time delays due to congestion, and presentation of accident information.

     

Advanced fleet management

 

Uses advanced vehicle routing algorithms that collect real–time congestion information to balance routes and loads, and predict travel times.

     

Alerts for ATIS messages

 

Refers to information presented to drivers prior to, or concurrent with, the presentation of an ATIS message. Alerts are typically used to notify drivers of high–priority ATIS messages associated with safety (e.g., immediate hazard, emergency vehicle approaching), vehicle status (e.g., vehicle condition warning), or augmented signage information (e.g., guidance, notification, or regulatory signs).

     

ASR

 

Automatic Speech Recognition

     

ATIS

 

Advanced Traveler Information Systems

     

ATIS design for special populations

 

Refers to design criteria aimed specifically at drivers with either sensory or cognitive disabilities that might affect their ability to effectively use the system. One such population is the older driver, over the age of sixty. There is a considerable body of research showing that the older population has numerous cognitive and sensory deficits. Other specialpopulations include handicapped or disabled drivers, as well as those people with minor cognitive impairments. In many cases, the suggestions made for improving ATIS design for these populations would increase its usability for the general population as well.

     

ATMS

  Advanced Traffic Management Systems
     

Auditory message length

 

Refers to the number of syllables, words, or sentences necessary for presenting auditory information to the driver. Depending on the type of information being presented, different message lengths are acceptable.

     

Augmented signage functions

 

Refers to transportation technologies that provide the user/driver with noncommercial routing, warning, regulatory, and advisory information that is currently presented on external roadway signs.

     

Automated toll collection

 

Refers to allowing a vehicle to travel through a toll roadway without stopping to pay tolls. Instead, tolls would be automatically deducted from the drivers accounts as they drive past toll collection areas. This would enable tolls to be adjusted to balance traffic flows (higher toll rate during peak rush hour). Also, automated toll collection would provide drivers with information regarding toll credits and the current toll costs.

     

Automated vehicle location

 

Employs GPS, or other triangulation technologies, to provide real–time information regarding the location and status of vehicles.

     

Automatic/manual aid request information

 

Refers to a function that allows the driver to request emergency services without leaving the vehicle. This function would provide drivers with immediate access to a wide variety of roadside assistance (e.g., police, ambulance, towing, and fire department) without the need to locate a phone, know the appropriate phone number, or even know their current location. In circumstances where a manual aid request is not feasible and where immediate response is essential, this function would activate automatically.

     

Automatic vehicle classification (AVC)

 

Employs EC technology to provide a readable, electronic record of vehicle type and contents.

     

Automatic vehicle classification/automatic vehicle identification (AVC/AVI)

 

Would allow uninterrupted movement of the vehicle through inspection or weighing stations.

     

AVL

  Automated Vehicle Location
     

CAS

 

Collision Avoidance System

     

CIE

 

Commission Internationale de l'Eclairage

     

CB Radio

 

Citizen's Band Radio

     

Clear depiction of route on electronic maps

 

Route information displayed on an electronic map must be clearly distinguishable from normal map features, in both route planning and guidance modes. In paper maps, a planned route can be clearly indicated by highlighting it with a colored marker. Similarly, on electronic maps, the user must be able to immediately discriminate the route from the variety of line shapes, sizes, and colors that may be used on the electronic map to depict local streets, arterials, highways, interstates, rivers and other features.

     

Color coding

 

Refers to the use of chromaticity to differentially identify items in a display systematically. The categories used to color code objects on a display depend upon the tasks required of the operators.

     

Color coding of traffic flow information

 

Refers to the use of colors to represent the mean speed of traffic flows on different road segments along a particular route. This type of information might help drivers make more informed decisions regarding alternate routes, departure times, or modes of transportation, if necessary.

     

Color contrast

 

Refers to the relationship between symbol and background associated with chromatic differences such as hue and saturation. Determining the amount of contrast provided to the driver becomes a more complex problem when the symbology and/or background are colored.

     

Command style messages

 

Refers to a message style that informs the driver of a situation and suggests a particular action to take in response to that situation.

     

Communication acknowledgment

  Refers to the capability of a CVO in–vehicle communication or messaging system to provide the sender of a message (i.e., a driver or a dispatcher) confirmation that a message was transmitted and received by the system hardware, and to provide information as to whether or not a message has been accessed or "opened" by the recipient.
     

Complexity of ATIS information

 

Refers to the number of information units being presented during written or textual in–vehicle road messages. In this context, an information unit can describe geography (e.g., city), type of roadway (e.g., highway), event causes (e.g., stalled vehicle), event consequences (e.g., traffic jam), time and distances, and proposed actions. Therefore, information units can be described as the relevant words in a message.

     

Control coding

 

Refers to the design characteristics of controls that serve to identify the control or to identify the relationship between the control and the function to be controlled. Proper coding of controls will increase the probability that the controls will be quickly and accurately located by drivers, thus reducing the eyes–off–road time.

     

Control movement compatibility

 

Refers to the expected relationships between control actuation movements, and the corresponding movements or change in the system being controlled. Making control movements consistent with the driver's expectations can decrease reaction and learning times, control errors, and can increase driver satisfaction with the vehicle's controls.

     

CRT

 

Cathode Ray Tube

     

CSRDF

 

Crew Station Research and Development Facility

     

CVO

 

Commercial Vehicle Operations

     

CVO–specific aid request information

 

Refers to the ability to notify emergency personnel (e.g., police, ambulance, towing, fire) of the need for aid. It may also include the ability to provide the driver with feedback regarding the status of emergency services. In the case of commercial vehicles, it may be especially important for emergency personnel to know specific information regarding the type of truck and the cargo it is carrying.

     

CVO–specific cargo and vehicle monitoring information

  Refers to more detailed and diverse information than that presented to private drivers. It may include a more precise indication of engine performance. In addition, many commercial vehicles carry sensitive cargo, which require careful monitoring of things like temperature, humidity, and vibration.
     

CVO–specific guidance sign information

 

Refers to sign information which might be helpful for guiding commercial vehicle operators to a particular destination. Such information is currently found on out–of–the–vehicle signage (e.g., truck route signs); however, this subfunction would allow this information to be presented to the commercial driver aurally, in the vehicle.

     

CVO–specific notification sign information

 

Refers to information regarding potential hazards and road changes. Particularly in the case of large trucks, additional time to plan or prepare for long/steep grades, sharp curves, exits, and lane changes may be valuable. Also, presenting this information in–vehicle may allow for it to be more detailed and timely.

     

CVO–specific regulatory administrative information

 

Refers to various regulatory administrative requirements, including taxes, licensing, permits, and coordination of the transport of hazardous materials. This function may also be involved with checking the required training programs and other administrative functions required of a CVO company by law.

     

CVO–specific regulatory sign information

 

Refers to information regarding size and weight limits, truck speed limits, and any road restrictions.

     

Design of ATIS subsystem interfaces

 

Refers to the consistency of the "look and feel" associated with the ATIS driver–vehicle interface (DVI), across various functions within the ATIS. For example, a single ATIS device could include trip planning, route guidance, travel coordination, and message transfer functions, much as modern computer systems include word processing, graphics, and e–mail applications. The degree of integration or consistency refers to the color schemes, fonts, layouts, and control operations associated with these different functions. A fully integrated system would have a common user interface, with the same colors, formats, and control operations; in a nonintegrated system, these features could vary from function to function.

     

Design of head–up displays for ATIS

  Refers to an electro–optical device that presents both static and dynamic symbology and/or graphics in the driver's forward FOV. Presenting navigation information to drivers through HUDs is possible due to recent developments in automotive design, electronic instrumentation, and optics.
     

Design of speech–based controls

 

Refers to systems that recognize human speech and treat speech commands as inputs to the ATIS system. Automatic speech recognition (ASR) systems may be characterized with respect to three sets of design characteristics.First, speaker–dependent systems recognize speech from only one speaker that has been calibrated to the system; speaker–independent systems can recognize speech from many speakers. Second, isolated word recognition systems require that speakers provide a pause or gap between words in a message; continuous speech recognition systems do not require any pause between words. Third, ASR systems vary with respect to the size of the vocabulary that they recognize.

     

Destination coordination information [CVO]

 

Refers to coordinating shipments with customers. This might involve making arrangements for loading and unloading shipments and catering to changes in scheduled pick–up and delivery times.

     

Destination coordination information

 

Refers to information which enables the driver to communicate and make arrangements with the final destination. This function may include making restaurant and hotel reservations. In addition, it may include ascertaining information about parking availability and location.

     

Destination preview

 

Refers to providing the user with the capability to recenter (slew) the map and to change the range scale (magnification) to enable full preview of route details. The user of an electronic map displaying route information may desire to preview the origin, destination, or any segment of the route.The system design should, however, distinguish clearly between a recentered map mode and the normal display mode showing current position of the user/vehicle. Failure to clearly distinguish between these two modes can result in confusion about current location.

     

DOT

  Department of Transportation
     

Driver/vehicle real–time safety monitoring

 

Could include records of duty logs, medical qualifications data, and commercial driver's license information. Vehicle –related elements could include operational data and conditional information (such as status of brakes, lights, tires, and steering).

     

Dynamic route selection information

 

Refers to any route selection function which is performed during the drive. The purpose of this ATIS function is to provide the driver with a mechanism for recovering once they have left or wandered from the intended route. When a driver makes a wrong turn and leaves the intended route, the dynamic route selection function can generate a new route which will accommodate the driver's current position.

     

DVI

 

Driver–Vehicle Interface

     

EC

 

Electronic Credentials

     

Electronic credentials

 

Would enable a motor carrier to electronically file for, obtain, and pay for all required licenses, registrations, and permits. An electronic record of the credential could be sent to the motor carrier's headquarters or other desired location.

     

Electronic log book

 

Could replace the manual trip log typically prepared by the motor carrier. The fuel tax rates for each state and the number of vehicle miles traveled within each state could be recorded electronically if electronic beacons were provided at all site boundaries.

     

Emergency vehicle information

  Refers to warning drivers of approaching emergency vehicles (i.e., police cars, fire trucks, ambulances). If the ATIS possesses reliable data on surrounding traffic and conditions, this function may also include telling the driver the appropriate action necessary to move out of the way.
     

Estimated time of arrival

 

Refers to the ability of a system to estimate the time remaining until a vehicle reaches the destination. In this context, ETA is simply the length of the route remaining to be negotiated divided by the average speed expected over the remaining route (e.g., ETA is 3 minutes, 15 seconds). It is common in some domains to add ETA to the current time to express estimated arrival time in clock time (e.g., a commercial aircraft might express their ETA as 7:30 p.m.). Accurate ETA information is critical to the effective deployment of emergency response vehicle fleets.

     

ETA

 

Estimated Time of Arrival

     

FHWA

 

Federal Highway Administration

     

Filtering sign information

 

Refers to allowing the driver to select the on–road signage they would like to receive in–vehicle. The driver will be able to filter both notification and guidance sign information. However, due to the importance of regulatory sign information, it will be presented to the driver regardless of preference.

     

Font segments

 

Refers to electronic displays in which characters are formed by illuminating discrete segments within a basic symbol pattern. The majority of electronic displays using this technique employ 7–segment patterns to generate numerals (e.g., digital speedometers and clocks); however, 14–segment and 16–segment patterns are also available for the generation of complete alphanumeric sets.

     

FMVSS

 

Federal Motor Vehicle Safety Standards

     

FOV

 

Field–of–View

     

Ganged controls

 

Refers to two or more knobs mounted on concentric shafts.

     

General trip planning information

  Refers to information which assists drivers in the coordination of long and/or multiple–destination journeys. Coordination of these journeys may involve identifying scenic routes and historical sites. However, the general purpose of this information is to provide the driver with an estimate of journey time, mileage, and costs.
     

GPS

 

Global Positioning System

     

Guidance sign information

 

Refers to information which helps to guide a driver to a particular destination. This information is normally found in the out–of–vehicle environment (e.g., street signs, interchange graphics, route markers, and mile posts). However, with augmented signage messages, this information will be brought into the vehicle and displayed to the driver.

     

Hazardous material information systems

 

Could provide enforcement and incident management response teams with timely, accurate information on cargo contents, enabling them to react properly in emergency situations.

     

HCI

 

Human–Computer Interaction

     

HDD

 

Head–Down Display

     

HOV

 

High Occupancy Vehicles

     

HUD

 

Head–Up Display

     

Immediate hazard warning information

 

Refers to information regarding the relative location of a hazard and the type of hazard. This information may include warning the driver of an accident immediately ahead or a stopped school bus. Thus, this information focuses on the location of specific localized incidents.

     

IMSIS

 

In–Vehicle Motorist Services Information Systems

     

Information units

 

This phrase is used to describe the amount of information presented in terms of key nouns and adjectives contained within a message.

     

IRANS

 

In–Vehicle Routing and Navigation Systems

     

ISIS

 

In–Vehicle Signing and Information Systems

     

ISO

 

International Standards Organization

     

ITS

 

Intelligent Transportation Systems

     

IVIS

 

In–Vehicle Information System

     

IVSAWS

 

In–Vehicle Safety and Warning Systems

     

Lane position information

 

Refers to information presented for the purpose of helping drivers avoid last minute lane changes. Providing the driver with a little extra lead time to make a lane change might be beneficial when driving an unfamiliar route or in circumstances where traffic is heavy and lane maneuvers may be difficult.

     

Level–of–service

 

A qualitative measure describing operational conditions within a traffic stream; generally described in terms of such factors as speed and travel time, freedom to maneuver, traffic interruptions, comfort and convenience, and safety.

     

LOS

 

Line–of–Sight

     

Message transfer function

 

Refers to the capability for drivers to communicate with others. Currently this function is accommodated with cellular phones and Citizen's Band (CB) radios; however, future ATIS systems may improve upon this technology. This function might include text and voice messages, however, it does not include the transmission of mayday calls. Likewise, this function is separate from the computer–aided dispatch function, but may be used with it.

     

Modality of ATIS information for CVO

 

Refers to the use of auditory and/or visual presentation modalities.

     

Motorist services functions

  Refers to transportation technologies that provide the user/driver with commercial logos and signing for motels, eating facilities, service stations, and other signing displayed inside the vehicle to direct motorists to recreational areas, historical sites, etc. Can also provide routing information for local destinations.
     

Notification sign information

 

Refers to information which notifies drivers of potential hazards or changes in the roadway. This information will be presented to the driver in–vehicle. Examples of this information will include: merge signs, advisory speed limits, chevrons, and curve arrows. In addition, notification information may include temporary or dynamic information such as road closures, road maintenance, or road construction. Other supplementary information, such as the distance to a notification point, may also be provided.

     

Notification style messages

 

Refers to a message style that simply informs drivers and allows them to determine the appropriate action on their own.

     

Number of control actions for commercial driver ATIS tasks

 

Refers to the number of control actions, such as button presses, required to complete a specific information retrieval task during ATIS operations while the vehicle is in motion.

     

Orientation of moving map displays

 

Refers to the angle that the map is rotated relative to the electronic display surface. Moving map displays may be oriented in a number of ways. The most common orientations are north–up and heading–up (sometimes referred to as track–up). Paper maps used by motorists are typically drawn north–up following traditional cartographic convention; that is, with true north being towards the top of the page. With a north–up moving map, the orientation of the symbol of the vehicle on the screen changes as the vehicle turns left and right; the symbol points toward the top of the map display only when the vehicle is pointing north. In contrast, with a heading–up map the vehicle symbol remains pointed towards the top of the screen regardless of the vehicle's heading. As the vehicle turns left and right, the map display rotates clockwise and counterclockwise, respectively, so that the symbol remains pointed towards the top of the screen. Variations of these two orientations are possible.

     

Pathway information

 

Refers to full or partial route information given to a driver.

     

Point of interest information

 

Refers to information presented to the driver that identifies scenic routes, historical sites, national parks, and recreational areas within a predetermined radius surrounding the route. Having this information will allow drivers to choose whether or not they wish to adjust their route and travel plans to include a specific point of interest. Other information that might be presented includes: states, regions, communities, and districts along the route.

     

Preference and directory information

 

Refers to information similar to that found in the yellow pages. However, unlike a yellow pages directory, the services/attractions directory has the flexibility of a computer database and would facilitate a wide variety of search methods. For instance, in searching for a shopping center, one parameter might be its physical location, which might be specified using an electronic map and touch screen. Providing the system with preference information allows it to assess information concerning businesses or attractions that satisfy the driver's current need.

     

Regulatory sign information

 

Refers to information found on out–of–vehicle signage which helps to regulate traffic and displays the rules of the road. This information will be presented to the driver in–vehicle. Examples of this information include: speed limit signs, stop signs, yield signs, turn prohibitions, and lane use control (e.g., left turn only).

     

Relationship between ATIS information and roadway signs

 

Refers to the correspondence or consistency between these two forms of presenting safety/warning information. Safety/warning information might be presented on roadway signs alone, on the ATIS alone, or on both display mediums.

     

R&D

 

Research & Development

     

Restriction information

 

Refers to weight, size, and cargo constraints, which might not concern private drivers, but could impact the travel plans of a commercial driver, perhaps even forcing them to choose an alternate route.

     

RGS

 

Route Guidance Simulator

     

RMS

  Root Mean Square
     

Road condition information

 

Refers to information relevant within some predefined proximity to the vehicle or its route. This information may include traction, visibility, congestion, construction activity, or weather conditions. Compared to the information conveyed by the immediate hazard information system, this function provides general information that could cover a wider geographic area and a longer time span.

     

Roadway information

 

Refers to information presented to a driver during trip planning. It may include the street or roadway names, the types of roads used, and the number of turns or roadway changes required along the route. This information will give drivers a general overview of the trip they are about to take, as well as familiarize them with the overall route.

     

Route and destination selection information

 

Refers to destination and route selection choices that the driver engages in when the vehicle is in park and when driving to one destination. The information provided by the system might include real-time or historical congestion information, estimated travel time, and routes that optimize travel on a variety of parameters.

     

Route guidance information

 

Refers to navigation directions in a turn–by–turn format. Route guidance provides information such as: distance to the next turn, the name of the street to turn onto, what lane to be in to make the turn, and the direction of the upcoming turn.

     

Route incident information

 

Refers to the data necessary for helping a driver travel to a selected destination when incidents are detected along the route.

     

Route schedulinginformation

 

Concerns the coordination of short, multiple–destination routes to minimize travel time or to minimize lateness on deliveries. Therefore, this function would take the driver's destination as input and provide an optimal order for traveling between destinations

     

Routing and navigation functions

 

Refers to transportation technologies that provide the user/driver with information about how to get from one place to another. When integrated with an Advanced Traffic Management System (ATMS), Routing and Navigation provides information on recurrent and non– recurrent traffic congestion and is capable of calculating, selecting, and displaying optimum routes based on real–time traffic conditions.

     

SAE

 

Society of Automotive Engineers

     

Safety/warning functions

 

Refers to transportation technologies that provide the user/driver with warnings of unsafe conditions and situations affecting the driver on the roadway ahead. Can also provide sufficient advanced warning to permit the driver to take remedial action, and provide messages related to relatively transient conditions, requiring modifications to the messages at irregular intervals.

     

Selection of colors for coding visual displays

 

Refers to the use of different colors either to bring information to the attention of a driver, or to aid the driver in distinguishing between items on a display. Color coding may be used to make absolute or relative discriminations, and should be used in a way that is redundant with other coding dimensions (e.g., shape, size, brightness).

     

Selection of control type

 

Refers to the apparatus by which the driver makes control inputs [i.e., push-buttons, push–pull knobs, rotary knobs (discrete and continuous), levers, slides, thumbwheels, toggle switches, or rocker switches]. Selection of appropriate control types is important to decisions regarding control location, because some control types are more suited to particular locations, and, conversely, particular locations are ideal for certain types of controls.

     

Selection of keyboards for ATIS devices

 

Refers to trade–offs and heuristics associated with fixed–function vs. variable–function keyboards. Examples of a fixed–function keyboard include cash register terminals and hand–held calculators; examples of a variable–function keyboard include keyboards for video games with different controls for different games, shifted keys of computer keyboards, and, in general, "soft " keys that can be changed via software control.

     

Sensory modality for presenting ATIS/CVO messages

 

Refers to the display modality most appropriate for presenting in–vehicle information to the driver. Almost all the literature on this topic suggests that operator performance can be improved by combining auditory and visual messages. These channels should be used together to provide either redundant or complimentary cues to the driver whenever possible. However, it is also important to know the advantages and disadvantages of using each of these modalities independent of one another so that when designers are faced with a choice, they can choose the modality that facilitates driver decision making and performance.

     

Services/attraction information

 

Refers to information provided to travelers which is normally found on commercial road signs or yellow pages. This information should not be provided unless specifically requested from the driver. However, the information presented can be filtered to present only those services/attractions which meet a certain profile of the driver's interests.

     

Service directory information

 

Refers to information similar to that found in the yellow pages or a Trucker's Atlas. However, the attraction/services directory has the flexibility of a computer database and would facilitate a wide variety of search methods, allowing CVO drivers to satisfy their current needs in the fewest number of stops.

     

Stacking messages

 

Refers to a practice in which, if two maneuvers are less than 10 seconds apart, the two instructions should be given together, prior to the first maneuver.

     

Symbol color

 

Color perception is derived from variations in the wavelength or spectral composition of light. Color perception can be described in terms of three psychological dimensions: hue, saturation, and brightness. Hue is related to the dominant wavelength of the stimulus, saturation is somewhat more loosely related to the spectral bandwidth of the stimulus, and brightness is related to the luminance of the stimulus.

     

Symbol contrast

 

Refers to the relationship between the luminance of a symbol and the luminance of the symbol's background.

     

Symbol font

 

Refers to the geometrical characteristics or style of symbology. Design goals for symbol font are to avoid extensive flourishes and embellishments of the symbols.

     

Symbol height

 

Refers to the vertical distance between the top and bottom edges of an unaccented letter or number. Since ATIS devices can be used at a broad range of display distances, symbol height is best defined and specified as the visual angle subtended by the symbology (at the driver's eye), in minutes of arc.

     

Symbol luminance uniformity

 

Refers to the consistency of luminance values across a display.

     

Symbol spacing

 

Refers to the horizontal space between adjacent characters on a display. Symbol spacing is often expressed as the ratio of space–between–characters to symbol–height (space–to–symbol–height ratio).

     

Symbol strokewidth–to–height ratio

 

Refers to the ratio of the symbol stroke thickness to symbol height.

     

Symbol versus text presentation of ATIS/CVO messages

 

Refers to the style and format of in–vehicle visual messages. A key ATIS/CVO design issue is the presentation of information to the driver so that it is not distracting and is easily understood. Symbols or icons are increasingly used in the design of electronic devices under the assumption that they are preferable to text (e.g., "a picture is worth a thousand words"). However, if drivers are unfamiliar with the symbol or if the symbol is not intuitive, it may be less effective than a corresponding text message when used in an ATIS/CVO device.

     

Symbol width–to–height ratio

 

Refers to the ratio of the width to the height of the symbology.

     

Tailoring of ATIS information to individual preferences

 

Refers to drivers' ability to personalize or to adjust ATIS design parameters to suit their individual driving habits, needs, and preferences.

     

Timing of auditory navigation information

 

Refers to the time or distance at which ATIS should present an auditory instruction to the driver before an approaching navigation maneuver (e.g., a required turn).

     

Travel coordination information

 

Refers to information regarding different modes of transportation (e.g., buses, trains, and subways) that may be used in conjunction with driving a vehicle. This information might include real-time updates of actual bus arrival times and anticipated travel times, and would allow coordination of multimode trips.

     

Trip scheduling information

 

Refers to information regarding each of the pick–up and delivery points along a predetermined route. This information aids in the coordination of long, multiple–stop journeys and allows drivers to double–check that the current route will optimize their delivery schedule.

     

Two–way real–time communications

 

Would provide ATIS and ATMS information to drivers or dispatchers concerning congestion, incidents, and optimum routing.

     

TWC

 

Two–Way Real–Time Communications

     

UCS

 

Uniform Chromaticity–Scale

     

UMTRI

 

University of Michigan Transportation Research Institute

     

User interface design

 

Refers to the system design characteristics of a computer-based system that includes the screen layout and format, selection of icons, use of borders and windows, control selection and placement, and the procedures and "rules" that define transactions between the system and the user.

     

VDT

 

Visual Display Terminal

     

Vehicle condition monitoring

 

Refers to the tracking of the overall condition of the vehicle to inform the driver of current problems as well as potential problems. Vehicular monitoring could range from reminding the driver to perform certain services (e.g., oil change) to warning the driver about current problems (e.g., engine overheating or flat tire). This system could also be interactive, allowing the driver to interrogate the system regarding the problem and possible solutions.

     

Vehicle location accuracy

 

Refers to the difference between the actual position of the vehicle and the position of the vehicle as presented by an ATIS or CVO device. Accuracy is a function of both the variability inherent to the method of determining the vehicle's position (e.g., differential GPS provides a more accurate position estimate than does raw GPS) and, in the case of a moving vehicle, the latency in determining the position. Error attributable to the position sensing system is often described as the ellipse (or circle) that contains the true position of the vehicle a known percentage of time. Typically, 95 percent or 99 percent is used as the criterion for the error envelope. The root mean square (RMS) error is an alternative method commonly used to describe the position error. Position error due to latency is a function of the update rate and the velocity of the vehicle. Assuming that the system is able to determine the position of the vehicle perfectly, a 1 second delay in updating the position of a vehicle traveling 100 kph (62 mph) results in an error of 27.8 meters (91 ft).

     

VFD

 

Vacuum Fluorescent Displays

     

Weigh in motion

 

Allows motor carriers equipped with special transponders to proceed on the highway at normal speeds through instrumented weigh stations as their weight is electronically inspected by in–pavement scales and readers.

     

WIM

 

Weigh in Motion

 

FHWA-RD-98-057

 

Previous | Table of Contents | Next

ResearchFHWA
FHWA
United States Department of Transportation - Federal Highway Administration