NATIONAL ADVANCED DRIVING SIMULATOR
NATIONAL ADVANCED DRIVING SIMULATOR

Introduction

The National Advanced Driving Simulator (NADS) is

the most sophisticated research driving simulator in the

world. Developed by the National Highway Traffic

Safety Administration (NHTSA), the NADS at The

University of Iowa offers the highest fidelity real-time

driving simulation experience.

The NADS’ primary mission is to conduct research that

will lead to a better understanding of the complex

driver-vehicle-roadway interaction in critical driving

situations. The results of this research will ultimately

lead to reductions in the number of traffic-related

deaths and injuries on the nation’s highways. The

NADS can also be used to conduct vehicle system

engineering research that will enhance the productivity

of the U.S. automotive manufacturing sector.

The NADS consists of a large, 24-foot-diameter dome

in which entire cars and the cabs of trucks and buses

can be mounted. Each vehicle cab is equipped

electronically and mechanically using instrumentation

specific to its make and model. At the same time, the

motion subsystem, on which the dome is mounted,

provides 64 feet of horizontal and longitudinal travel and

330 degrees of rotation. The effect is that the driver

feels acceleration, braking and steering cues as if he or

she were actually driving a real car, SUV, truck, or bus.

The latest in visual display technology, coupled with a

high-fidelity audio subsystem, completes the driving

experience. The driver is immersed in sight, sound and

movement so real that impending crash scenarios can

be convincingly presented with no danger to the driver.

Vehicle and driver data are collected and stored, and

tests can be reproduced. A simulator operator and a

researcher control the entire system and provide for

the full safety and protection of the driver and

equipment during operation.

A world-class team of leaders in simulation technology

developed and built the NADS, which is now operated

and maintained by a University of Iowa team of highly

qualified researchers with a combined total of more

than 100 years of simulation and research experience.

The NADS is located at The University of Iowa

Oakdale Research Park in Iowa City, Iowa. The

University of Iowa was selected in a national

competition, among major transportation research

universities, conducted for NHTSA by the National

Science Foundation. The University of Iowa provided

$11.58 million in cost sharing to the NADS project,

which included the development of software and the

design and construction of a $5.7 million building to

house the simulator.

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NADS Facility at The University of Iowa

A Look Inside the NADS Dome
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The NADS Facility

The NADS facility is comprised of a controlledaccess, high-bay area that houses the device, the

Simulation Development Module (SDM), an operator

control room, and a large cab storage and

preparation area. These technical resources are

within yards of three participant preparation and

briefing rooms and a fully equipped medical room

used for studies that require examinations, drug

administrations or participant monitoring. The entire

area is secure to ensure confidentiality and privacy.

Operator and Research Workstations

Two main operator and research workstations, for the

simulator operator and the guest researcher, are in

the NADS control room and overlook the simulator

bay through large glass panels. These workstations

include multiple large-screen display monitors that

can simultaneously present video and digital data.

Workstation operators can select, monitor and record

numerous experimental parameters. Additional video

monitors are used to view a sequence from the

driver’s perspective. Headphones and speakers allow

direct communication between simulator operators

and the driver. All data are recorded and up to five

data elements may be selected during run-time for

display on a workstation. Simulator monitor and

control software provide the operator with the control

and status information needed for efficient and safe

conduct of the simulation.

Program Planning and General Operations

As a national resource for carrying out critical

highway safety research, The University of Iowa is

responsible for operating and maintaining the NADS

facility, as well as scheduling government and private

sector usage.

Prior to scheduled experiments, NADS researchers

team with experienced software, visual display, and

hardware engineers to:

• Prepare a detailed experimental plan;

• Define the scenario;

• Plan software model changes, if necessary, or

include models supplied by researcher;

• Plan for data collection and reduction; and

• Plan for the recruiting and preparation of study

participants.

All software and databases developed specifically for

an experiment are protected and kept isolated from

other researchers. Data security is provided to ensure

that proprietary rights are protected to the extent

permitted by law.

Before actually conducting an experiment on the

NADS, the staff and researchers develop and test

scenarios, verify the accuracy of the expected data

flow, test any necessary special equipment and

obtain approval for use of “human subjects” in a

particular study. Next, participants for the study are

contacted and scheduled. Finally, a cab is configured

in the NADS, and all software files and databases are

Medical-Equipped Participant Room

Operator Control Room
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loaded and prepared for the experiment. A library of

generic scenarios and city/rural databases is

maintained for research in areas that do not require

unique properties and characteristics. Daily

operational readiness tests are conducted to ensure

that systems are safe and ready for use prior to

conducting experiments.

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Tile Mosaic Tool for driving scene databases

Vehicle Selection Interface 

Following an experiment, the NADS staff assists with

data reduction and analysis, depending on the

researcher’s needs.

Simulation Development Module

In addition to the NADS, the facility incorporates a

Simulation Development Module. The SDM is a fixedbase simulator with a 120-degree field-of-view

screen. Each of the available cabs can be installed in

the SDM, and the system can replicate the NADS

visual environment. The SDM is used to support

development and testing of experimental procedures

and protocols, including pilot testing of scenarios and

training of study participants. This allows for

refinement of the scenarios and procedures, and

provides a low-cost means of setting up and tuning

experiments prior to running experiments on the

NADS, thereby greatly reducing development and

other experimental costs.

Scenario Definition & Control

The NADS facility includes an extensive, softwarebased simulation development environment (including

tools such as the Tile Mosaic Tool, the Interactive

Scenario Authoring Tool, and data reduction

workstations) for developing new, or modifying
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Interactive Scenario Authoring Tool

existing, experimental scenarios, special databases

(visual, audio, roadways), and data reduction

procedures. This software allows a researcher to

precisely plan the interactions of the subject vehicle

with an elaborate set of scenes and objects. The

researcher can also define and control a large set of

driving environments - including condition and type of

roadway, companion and opposing traffic, traffic

control devices and traffic incidents. In addition, the

researcher can modify vehicle models populating

traffic (e.g., heavy trucks, emergency vehicles) for

specific research and develop applications for

experimental data collection, reduction and analyses.

System Safety

Ensuring the safety of the study participant is

paramount, and the NADS design provides multiple

levels of safety controls to protect the driver. During

operation, the participant, operator or researcher can

halt the simulation at any time. In addition, each

motion subsystem contains its own safety monitoring

functions to prevent injury to the driver in case of

malfunction. The NADS also includes an

independent, fully redundant safety monitoring

system. This system prevents activation of the

simulator, or aborts operation of the simulator, if any

potentially hazardous situation exists, or any

anomalous system behavior is detected.

NADS Subsystems

The NADS contains a number of subsystems that

provide the driver with a realistic representation of the

driving environment. These subsystems work in real

time to provide repeatable, natural and realistic

representations of the visual, motion, auditory and

control feel sensory cues associated with the

complete driving experience.

Visual Subsystem

The NADS visual subsystem brings together multiple

detailed terrain and driving databases with the latest

advances in high-resolution imagery. This subsystem

incorporates a 24-foot-diameter dome with a high

gain screen and utilizes 15 LCD (Liquid Crystal

Display) projectors with high resolution that generate

the highly realistic images. Other features of the

visual subsystem include:
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Graphical depiction of typical scene from the

forward view.

Motion Subsystem

The motion subsystem provides a combination of

translational and angular motion that duplicates

vehicle motion kinematics and dynamics within six

degrees of freedom. The motion subsystem is

coordinated with the vehicle cab subsystem and its

high-frequency road feel and control feel subsystem

to provide the driver with realistic motion and tactile

cues while driving. This subsystem is designed to

provide drivers with highly accurate motion cues in all

Design Specifications of the 

NADS Visual Subsystem

Element Performance

Polygons (at 60 Hz) > 15,000

Total Pixels > 5 M

Transport Delay ≤ 50 ms (at 60 Hz)

Contrast Ratio 25:1

Luminance 5 fL

Field of View 360 deg H x 40 deg V

With High 

Resolution Inset 28 deg H x 7 deg V

Forward Inset - 

High Resolution 2.2 ArcMin/Line Pair

Forward and Side Area

Resolution 7.0 ArcMin/Line Pair

Rear Area and 

Rear-View Mirror

Resolution 15.0 ArcMin/Line Pair

• Multiple-channel projection system that provides

complete front and rear field of view, including use

of actual vehicle mirrors

• Rapid database generation for scenario

development

• Multiple eye points, view points and display

channels

• Complex 3-D imagery with full-color, textured

buildings, pedestrians, vegetation and other

environmental objects

• Complex 3-D imagery fully correlated with other

sensory stimuli

• Animation involving numerous objects that create

busy traffic situations with:

— Independent control rules and logic for

animation of other vehicles, pedestrians, scene

features and roadways, and

— Collision detection for all objects

• Visual subsystem database that includes the full

range of:

— Current and new highway traffic control devices

(signs and signals);

— Three-dimensional objects that vehicles

encounter (animals, potholes, concrete joints,

pillars, etc.);

— High-density, multiple-lane traffic interacting

with the driver’s vehicle;

— Common intersection types (including railroad

crossings, overpasses, bridge structures,

tunnels, etc.); and 

— Roadway time of day and complete

complement of environmental and atmospheric

effects
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Design Specifications of the 

NADS Motion Subsystem

Element Performance

X-Y Platform

Displacement ± 32 ft

Velocity ± 20 ft/s

Acceleration ± 20 ft/s2

Motion Base

Z (heave) ± 2.0 ft

Z (velocity) ± 5.0 ft/s

Z (acceleration) ± 25 ft/s2

Pitch ± 25 deg

Pitch rate ± 45 deg/s

Roll ± 25 deg

Roll rate ± 45 deg/s

Yaw (turntable) ± 330 deg

Yaw rate ± 60 deg/s

Pitch, Roll, Yaw accelerations ± 120 deg/s2

High Frequency Vibration

Displacement ± 0.2 in

High Frequency Envelope 3 Hz - 20 Hz

High Frequency Vibration

Acceleration ± 1000 lbf

Noise (Multi-axis) < 0.02 g rms

Design Specifications of the 

NADS Cab Subsystem

Element Performance

Control Feel Bandwidth > 50 Hz

Weight < 3,300 lbs

Cab Changeout Time < 8 hrs

a standard sedan (Chevrolet Malibu), a sports/utility

vehicle (Jeep Cherokee), a midsize sedan (Ford

Taurus), and a commercial truck cab (Freightliner).

Featured in the vehicle cab subsystem are interfaces

that allow rapid cab changes to meet desired

efficiency standards during NADS operations. The

dome can be reconfigured to accommodate and

operate a different cab in less than eight hours. The

vehicle cab subsystem incorporates a full range of

vehicle instrumentation interfaces, including fully

functioning controls, dashboard, seating and even an

operable radio/entertainment system.

Of particular note is the Eaton truck transmission

simulator, incorporated into the Freightliner cab,

which can be used to create heavy vehicle scenarios

from:

• 140 transmissions,

• 280 engines,

• 33 drive axle ratios, and 

• 300 tire sizes.

Additional technology, such as wireless communications, can be incorporated into the vehicle cabs to

address specific experimental requirements. In

addition, the cab design provides remarkably realistic

action and feel for the primary controls (steering,

brakes, accelerator) and transmission, and the

associated control logic is tunable to allow the

simulation of actual or proposed vehicle responses.

axes associated with actual vehicle motions for the

full range of driving maneuvers.

Key features of the NADS motion subsystem include:

• Isolated, high-frequency, self-reacting cab

vibration actuators that faithfully reproduce road

feel

• A turntable allowing ±330 degrees of rotation

• A design that allows for low maintenance costs

and minimal staffing requirements

Vehicle Cab Subsystem

The vehicle cab subsystem currently consists of four

vehicle cabs, configured to fit within the physical

environment of the visual dome on the motion

subsystem and provides the driver with realistic

vehicle controls. Each cab retains the interior of the

actual vehicles with few changes to the internal

ergonomics and layout. The four vehicle cabs include
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Available Vehicle Cabs 

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NATIONAL ADVANCED DRIVING SIMULATOR

Vehicle Cab Interiors

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Control Feel Subsystem

The control feel subsystem for steering, brakes,

clutch, transmission shift and throttle provide realistic

feedback in response to driver inputs, vehicle motions

and road/tire interactions. The control feel subsystem

is capable of representing automatic and manual

control characteristics such as power steering,

existing and experimental drive trains, anti-lock

braking systems and cruise control. The control feel

cuing feedback has high bandwidth and no

discernible delay or distortion associated with driver

control actions or vehicle dynamics.

Auditory Subsystem

The auditory subsystem provides motion-correlated,

directional sound sources via multiple in-cab

electrostatic speakers. These sound sources are

coordinated with the full range of the visual sensory

systems database. The auditory database includes

Design Specifications of the 

NADS Audio Subsystem

Element Performance

Dynamic Range 100 db

Bandwidth 15 Hz - 20 KHz

S/N Ratio 96 db

Distortion ≤ 1.0 %

Dynamic Synch < 28 ms

sounds emanating from current and new design

highway surfaces, from contact with three-dimensional

objects that vehicles encounter (potholes, concrete/tar

joints, pillars, etc.), from high-density multiple-lane

traffic (including city effects, sirens, tunnel passage),

from the vehicle during operation, and sounds that

reflect roadway changes due to changes in the

weather environments (including wind).

Vehicle Dynamics

The vehicle dynamics software properly represents

vehicle motions and control feel conditions in

NADS Vehicle dynamics software - Tire and Brake

Failure Dialog Screen.
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response to driver control actions, road surface

friction conditions and aerodynamic disturbances. The

vehicle dynamics software incorporates a multi-body

vehicle dynamics model that accurately simulates the

motion and feel of vehicle linkages and joints.

All required vehicle responses are computed in real

time for driving the visual, motion, cab, control feel

and auditory subsystems. The vehicle dynamics

models cover light passenger cars and trucks, and

heavy trucks and buses. The models encompass

normal driving conditions and limit performance and

maneuvering that might be encountered during precrash avoidance situations, including spinout and

incipient rollover.

NADS Research Uses

The unique capabilities of the NADS lend themselves

to studies that could not otherwise be safely carried out

on the open road. In particular, the ability of the NADS

to create highly complex but realistic scenarios, typical

of actual driving situations, in a highly controlled and

repeatable experimental setting allows researchers to

address a wide range of issues. The ability to impose

realistic demands on drivers, including those

associated with in-vehicle tasks, traffic conditions,

sudden events and environmental conditions (e.g.,

roadway, visibility), provide research opportunities not

possible on test tracks or the open road.

The NADS offers a safe, accurate and repeatable

environment for researchers to study human factors

issues associated with driver error, which are

estimated to be a contributing cause in 90 percent of

motor vehicle crashes.

The NADS is a unique research tool that offers the

capability to study driver crash avoidance behavior

and carry out related crash reconstructions. The

complete control of highway environment and traffic

scenarios provided by the NADS allows researchers

to: 1) set up hazardous driving situations and measure

driver response; 2) examine conditions associated

with real crash cases; and 3) study driver and vehicle

response options and limitations. A clear understanding of driver behavior under these circumstances

can lead to the development of effective strategies

and countermeasures for improved crash avoidance

and to reduce injuries and fatalities.

The NADS also provides the capability for safely

evaluating advanced in-vehicle systems and control

technologies. Important questions regarding the

effects of these systems on driver workload, attention,

behavior and overall safety are best addressed during

the development phase. It is imperative to determine

before the production phase if any of these advanced

systems will have an unintended or adverse impact

on driver performance and highway safety.

The NADS can also be used for conducting highway

engineering and design research related to traffic

safety. In the NADS’ synthetic environments, the

driving scene and highway geometry are under the

complete control of the simulation programmer.

Highway researchers can therefore evaluate
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alternative designs for intersections, entrances and

exits, tunnel and bridge alignments, traffic control

devices and highway signing without incurring the

prohibitive expense of actual construction.

The benefits of NADS research extends further to the

automotive industry, where the results, in combination

with those from simulators developed within the

industry, are used in the development and testing of

new safety devices.

The NADS is also an ideal tool to study the effects of

alcohol, drugs, visual impairments and aging on

driving. Medical and pharmaceutical researchers,

among others, use the NADS to investigate the safety

and efficacy of new medicines and medical devices in

the driving environment.

Summary

As the world’s most sophisticated research driving

simulator, the National Advanced Driving Simulator

offers easy experiment setup, product integration and

data collection. The NADS is the first to employ a

large motion base, capable of physically moving 64

feet in two directions, and providing users with true,

realistic motion experience, whether accelerating,

turning or braking. Its computer image generation

system features 15 LCD projectors that provide a

360-degree horizontal field of view and incorporates a

database of driving scenes spanning more than

2,500 square miles of terrain. Four vehicle cab types

are available for use, as well as multiple secure

participant briefing rooms and a medically equipped

facility for medical studies. In addition, The University

of Iowa offers a highly trained and experienced

technical and research team to work with researchers

on all aspects of research planning, development,

execution and analysis efforts.

This highly realistic driving simulator provides a

powerful tool for evaluating driver behavior in a wide

range of complex situations that would otherwise be

difficult, costly and often unsafe to obtain under

actual roadway driving conditions. Representative

traffic scenarios can be examined safely with

experimental repeatability, easy configurability and

comprehensive data collection capability. The level of

fidelity allows researchers to implement virtually any

experiment that they would consider in a real vehicle on

any roadway.

The NADS is dedicated primarily to advancing the

cause of improved highway safety. As a national

research facility, operated and maintained by The

University of Iowa, the simulator is accessible to the

widest possible spectrum of researchers from both the

public and private sectors. NHTSA, as well as

researchers from academic and medical institutions and

the automotive/transportation industries, uses the

NADS to study the total driver-vehicle-traffic

environment system with an eye to improving products,

highway designs, and reducing the causes of crashes -

in addition to reducing fatalities.

For more information, please contact:

Ginger Watson

NADS - Chief Application Scientist

The University of Iowa

2401 Oakdale Blvd., Iowa City, IA 52242-5003

319-335-4679 gwatson@nads-sc.uiowa.edu

Yiannis Papelis

NADS - Chief Technical Officer

The University of Iowa

2401 Oakdale Blvd., Iowa City, IA 52242-5003

319-335-4597 yiannis@nads-sc.uiowa.edu

L. D. Chen

NADS - Director 

The University of Iowa

2401 Oakdale Blvd., Iowa City, IA 52242-5003

319-335-4851 ldchen@nads-sc.uiowa.edu

Mike Goodman

NHTSA Advanced Research and Analysis 

Chief of the Driver Behavior Research and Simulation Division

400 Seventh Street, S.W., Washington, DC 20590

202-366-5677 mike.goodman@nhtsa.dot.gov

H. Keith Brewer

NHTSA Advanced Research and Analysis 

Dir. of the Office of Advanced Safety Research

400 Seventh Street, S.W., Washington, DC 20590

202-366-5671 kbrewer@nhtsa.dot.gov

NADS WEB INFORMATION 

www.nads-sc.uiowa.edu

www-nrd.nhtsa.dot.gov June 2002