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This paper describes a human factors simulation study of the decision making behavior of drivers attempting to avoid nonrecurring congestion by diverting to alternate routes with the aid of in-vehicle navigation systems. This study is the first phase of a two part project in which the second phase will apply the driver behavior data to a simulation model analysis of traffic flow. The object of the driver behavior experiment was to compare the effect of various experimental navigation systems on driver route diversion and alternate route selection. The experimental navigation system configurations included three map based systems with varying amounts of situation information and a non map based route guidance system. The overall study results indicated that navigation system characteristics can have a significant effect on driver diversion behavior, with better systems allowing more anticipation of traffic congestion.

Lateral/directional dynamics involve vehicle yawing, rolling and lateral translation motions and dynamic stability concerns directional behavior (i.e. spinout) and rollover. Previous research has considered field test and computer simulation methods and results concerning lateral/directional stability. This paper summarizes measurements and simulation analysis of a wide range of vehicles regarding directional and rollover stability. Directional stability is noted to be strongly influenced by lateral load transfer distribution (LTD) between the front and rear axles LTD influences tire side force saturation properties, and should be set up so that side forces at the rear axle do not saturate before the front axle under hard maneuvering conditions in order to avoid limit oversteer and spinout.

This paper describes a low cost, PC based driving simulation that includes a complete vehicle dynamics model (VDM), photo realistic visual display, torque feedback for steering feel and realistic sound generation. The VDM runs in real-time on Intel based PCs. The model, referred to as VDANL (Vehicle Dynamics Analysis, Non-Linear) has been developed and validated for a range of vehicles over the last decade and has been previously used for computer simulation analysis. The model's lateral and longitudinal dynamics have 17 degrees of freedom for a single unit vehicle and 33 degrees of freedom for an articulated vehicle. The model also includes a complete drive train including engine, transmission and front and rear drive differentials, and complete, power assisted braking and steering systems. A comprehensive tire model (STIREMOD) generates lateral and longitudinal forces and aligning torque based on normal load, camber angle and horizontal (lateral and longitudinal) slip.

This paper considers ground vehicle lateral/directional stability which is of primary concern in traffic safety. Lateral/directional dynamics involve yawing, rolling and lateral acceleration motions, and stability concerns include spinout and rollover. Lateral/directional dynamics are dominated by tire force response which depends on horizontal slip, camber angle and normal load. Vehicle limit maneuvering conditions can lead to tire force responses that result in vehicle spinout and rollover. This paper describes accident analysis, vehicle testing and computer simulation analysis designed to give insight into basic vehicle design variables that contribute to stability problems. Field test procedures and results for three vehicles are described. The field test results are used to validate a simulation model which is then analyzed under severe maneuvering conditions to shed light on dynamic stability issues.

An over-the-road study of driver destination entry using an example in-dash GPS-based navigation system was accomplished in traffic on urban surface streets and freeways. The evaluation used typical drivers, and a vehicle instrumented to record driver control inputs, vehicle response motions including lateral lane position, and driver eye glances and fixations. The primary task was to follow the routes in a safe manner, while moving with traffic and maintaining speed and lateral lane position. As a secondary task, the drivers entered the successive destinations while driving, using a touch screen, and at their own pace. They were told there was no hurry, nor was there a need to enter the destination quickly. Results are shown for number of keystrokes, total fixation times, number of fixations on the device, fixation duration, lane keeping performance, and subjective ratings related to ease of destination entry.

A tire/terrain interaction model is presented to support the dynamic simulation of off-road ground vehicle. The model adopts a semi-empirical approach that is based on curve fits of soil data combined with soil mechanics theories to capture soil compaction, soil shear deformation, and soil passive failure that associate with off-road driving. The resulting model allows the computation of the tire forces caused by terrain deformation in longitudinal and lateral direction. This model has been compared with experimental data and shown reasonable prediction of the tire/terrain interaction.

Basic performance properties of tires significantly influence the lateral/directional (steering) stability and handling of highway vehicles. These properties include cornering stiffness and peak and slide coefficients of friction. This paper considers some detailed tire machine measurements of lateral tire performance. A large database of tire properties for a wide range of highway vehicles is also analyzed. A regression analysis approach is used to define the sensitivity of various size and operational (speed, pressure and load) characteristics on tire behavior. The paper discusses the manner in which these properties vary with tire size and operational conditions, and the effect of the properties on vehicle stability and handling.

This paper describes the driver/vehicle modeling aspects of a computer simulation that can respond to highway engineering descriptions of roadways. The driver model interacts with a complete vehicle dynamics model that has been described previously. The roadway path is described in terms of horizontal and vertical curvature and cross slopes of lanes, shoulders, side slopes and ditches. Terrain queries are made by the vehicle dynamics to locate tires on the roadway cross-section, and to define vehicle path and road curvature at some distance down the road. The driver model controls steering to maintain lateral lane position. Speed is maintained at a speed limit on tangents, and decreased as needed to maintain safe lateral acceleration. Because the bandwidth of longitudinal (speed) control is much lower than lateral/directional (steering) control, the driver model looks further ahead for speed control than for steering.

Vehicle handling and stability are significantly affected by inertial properties including moments of inertia and center of gravity location. This paper will present an analysis of the NHTSA Inertia Database and give regression equations that approximate moments of inertia and center of gravity height given basic vehicle properties including weight, width, length and height. The handling and stability consequences of the relationships of inertial properties with vehicle size will be analyzed in terms of previously published vehicle dynamics models, and through the use of a nonlinear maneuvering simulation.

This paper describes a laboratory simulation study of driver reaction to in-vehicle navigation systems. The study included a pre-test questionnaire on demographic background and commuting behavior, simulation testing of navigation decision making, and a post-test questionnaire on navigation behavior and reactions to in-vehicle navigation systems and the laboratory simulation. A total of 277 subjects, both male and female, were employed over a wide range of ages. Test subjects were assigned to one of four navigation system groups or a no-system control group for the purpose of comparing system performance. The simulation task required subjects to experience a commuting ‘drive’ on a Southern California freeway route and minimize trip time by diverting off the main route to avoid congestion. Subjects were given orientation and training on the simulation and their navigation system condition, and were motivated by rewards and penalties to minimize trip time.

This paper describes validation work carried out for two vehicle dynamics computer simulation programs. One program, referred to as VDANL (Vehicle Dynamics Analysis NonLinear), is intended to simulate passenger cars, vans and light trucks. The second program simulates All Terrain Vehicles (ATVs) and is referred to as NLATV (NonLinear ATV). The programs have been checked out and validated for a variety of maneuvering conditions and a broad range of vehicles. The programs run on IBM-PC/MS DOS compatible computers, and numerical methods have been used to give numerically stable solutions with reasonable computational speed over a broad range of maneuvering situations.

Motion cueing algorithms can improve the perceived realism of a driving simulator, however, data on the effects on driver performance and simulator sickness remain scarce. Two novel motion cueing algorithms varying in concept and complexity were developed for a limited maneuvering workspace, hexapod/Stuart type motion platform. The RideCue algorithm uses a simple swing motion concept while OverTilt Track algorithm uses optimal pre-positioning to account for maneuver characteristics for coordinating tilt adjustments. An experiment was conducted on the US Army Tank Automotive Research, Development and Engineering Center (TARDEC) Ride Motion Simulator (RMS) platform comparing the two novel motion cueing algorithms to a pre-existing algorithm and a no-motion condition.

A class of driver attentional workload metrics has been developed for possible application to the measuring and monitoring of attentional workload and level of distraction in actual driving, as well as in the evaluation and comparison of in-vehicle human machine interface (HMI or DVI) devices. The metrics include driver/vehicle response and performance measures, driver control activity, and driver control models and parameters. They are the result of a multidisciplinary, experimental and analytical effort, applying control theory, manual control, and human factors principles and practices. Driving simulator and over-the-road experiments were used to develop, confirm, and demonstrate the use of the metrics in distracted driving situations. The visual-manual secondary tasks used in the study included navigation destination entry, radio tuning, critical tracking task, and a generic touch screen entry task.

Real time man-in-the-loop simulation can be used in a variety of research, testing and training roles where safety, efficiency and/or economy are important. Simulation can allow complete control and uniformity over driving conditions and permit analysis of a range of vehicle and driver behavior variables. Simulation complexity and fidelity requirements will vary depending on application requirements. This paper reviews past and current driving simulation development efforts and applications. Simulation requirements are assessed relative to various applications, including vehicle handling, driver behavior, training, licensing and fitness for duty testing.

Automatic and four wheel steering control laws are often developed from the performance point of view to optimize rapid response. Under linear tire operating conditions (i.e., maneuvering at less than .5g's) both performance and safety conditions can be simultaneously met. Under severe operating conditions, such as might be encountered during crash avoidance maneuvering, tire characteristics can change dramatically and induce directional dynamic instability and spinout. The challenge in automatic and four wheel steering system design is to achieve a compromise between performance and safety. This paper will describe analyses carried out with a validated vehicle dynamics computer simulation that shed some light on the vehicle and control characteristics that influence tradeoffs between performance and safety. The computer simulation has been validated against field test data from twelve vehicles including passenger cars, vans, pickup trucks and utility vehicles.

Ground vehicle dynamic stability, including spinout and rollover, is highly dependent on maneuvering conditions and the nonlinear force response characteristics of tires. Depending on vehicle configuration, unstable behavior requires high, sustained lateral acceleration, and some maneuver induced excitation of the roll and yaw mode dynamics. Dynamic instability in some vehicles can be induced by a steering reversal maneuver that involves sustained limit performance lateral acceleration. Using a validated vehicle dynamics simulation, analysis is presented to illustrate what constitutes a critical stability sensitive maneuver. Two example test cases are used to show that a critical stability sensitive maneuver must be more severe than a single lane change. Even reaching tire saturation limits during an aggressive single lane change does not give the sustained lateral acceleration required to provoke instability conditions.

A study of the effect on driver behavior and performance of varying occlusion parameters and secondary task duration was accomplished using the Dynamic Research, Inc. (DRI) Driving Simulator. Driver glance behavior and performance under comparable primary and secondary task conditions that were driver paced (no occlusion) were studied also. Both occlusion goggles and screen blanking means to interrupt vision were investigated. The several experimental phases included baseline primary driving task only, baseline secondary task only (no occlusion), secondary task with occlusion or screen blanking, primary driving task with goggles occlusion, and primary and secondary tasks combined, driver paced, with no occlusion or screen blanking. The secondary task human-machine interface (HMI) was a generic alpha entry task using a touch screen, located high in the center console.

Computer simulation and real-time, interactive approaches for analysis, interactive driving simulation, and hardware-in-the-loop testing are finding increasing application in the research and development of advanced automotive concepts, highway design, etc. Vehicle dynamics models serve a variety of purposes in simulation. A model must have sufficient complexity for a given application but should not be overly complicated. In interactive driving simulation, vehicle dynamics models must provide appropriate computation for sensory feedback such as visual, motion, auditory, and proprioceptive cuing. In stability and handling simulations, various modes must be properly represented, including lateral/directional and longitudinal degrees of freedom. Limit performance effects of tire saturation that lead to plow out, spin out, and skidding require adequate tire force response models.

Interactive simulation requires providing appropriate sensory cuing and stimulus/response dynamics to the driver. Sensory feedback can include visual, auditory, motion, and proprioceptive cues. Stimulus/response dynamics involve reactions of the feedback cuing to driver control inputs including steering, throttle and brakes. The stimulus/response dynamics include both simulated vehicle dynamics, and the response dynamics of the simulation hardware including computer processing delays. Typically, simulation realism will increase with sensory fidelity and stimulus/response dynamics that are equivalent to real-world conditions (i.e. without excessive time delay or phase lag). This paper discusses requirements for sensory cuing and stimulus/response dynamics in real-time, interactive driving simulation, and describes a modest fixed-base (i.e. no motion) device designed with these considerations in mind.

A simulator intended for driver/vehicle applied research and driver behavior studies is described. Designed and developed by Dynamic Research, Inc. in Torrance, CA, it features a 180 deg forward field of view, an animated graphics roadway scene, modular vehicle dynamics models, instrumented cabs with steering control loaders and aural cueing, an electrohydraulic hexapod motion base with ±2 ft of stroke in each leg, and system operation and data acquisition functions. Automobile and motorcycle cabs are available. Studies to date have considered steering and pedal controls layout, high speed brake in turn, and driver workload related to the use of an in-dash navigation and route guidance system.