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Wet Tire Testing
NHTSA conducted wet tire testing in support of research to examine ESC effectiveness on wet pavement.

Examination of the Distraction Effects of Wireless Phone Interfaces Using the National Advanced Driving Simulator
NHTSA conducted research to investigate the effects of wireless phone use on driving performance and behavior. The main objectives were to assess: 1) the distraction potential of wireless phone use while driving, and 2) the difference in distraction caused by the use of a hands-free wireless phone interface versus that associated with use of a hand-held interface.

Investigation of Driver Reactions to Tread Separation Scenarios in National Advanced Driving Simulator (NADS)
A study was conducted to investigate drivers’ reactions to tread separation scenarios using the National Advanced Driving Simulator (NADS). The objectives were to evaluate the effects of vehicle understeer gradient, prior knowledge of an impending tire failure, instructions on how to respond to a tire failure, driver age, and failed tire location on drivers’ responses and the likelihood of control loss following simulated tread separation on one of the rear tires of a simulated SUV traveling at high speed.

One hundred and eight (108) subjects experienced two tire failures while driving on a straight divided highway at approximately 75 mph with light surrounding traffic. Subjects were divided equally into three age groups (18-25, 35-45, 55-65) and gender was balanced. Drivers were assigned to one of three understeer conditions. Understeer conditions were referred to as Vehicle 1 (understeer gradient of approximately 4.7 deg/g ), Vehicle 2 (3.4 deg/g), and Vehicle 3 (2.4 deg/g). Following left rear tire detread, the understeer gradients resulting from a right turn changed to 1.10, 0.09, and –1.17 deg/g, respectively. The first tire failure was unexpected. The second tire failure was expected, with half of the subjects being given specific instructions on how to respond to a tire failure and the other half were told only that one or more tire failures would likely occur.

Decreasing vehicle understeer was strongly associated with the likelihood of control loss following both the unexpected and expected tire failures. Knowledge of the imminent tread separation reduced the overall probability of control loss from 55% to 20% and had a significant effect on how quickly drivers responded as well as on the nature of their initial responses (i.e., steering or braking). Driver age was marginally associated with increased likelihood of vehicle control loss, but only on unexpected trials. Vehicle speed at the time of first steering input also contributed to the probability of control loss. Neither the location of the tire that failed (left rear vs. right rear) nor the specific instructions about how best to respond to the tread separation influenced the probability of control loss. Differences associated with vehicle understeer conditions observed in the present study were large and consistent, independent of driver expectations and across driver age groups. It is thus fair to conclude that in the event of a complete rear-tire detread, the increased difficulty in vehicle handling and the associated increased likelihood of loss of vehicle control with decreasing vehicle understeer generalize to real-world driving.

A complete description of the methods used and results of this research are contained in the NHTSA report, "Investigation of Driver Reactions to Tread Separation Scenarios in National Advanced Driving Simulator (NADS)" DOT HS 809 523" released in January, 2003.

Support for National Advanced Driving Simulator (NADS) Development

  • The National Advanced Driving Simulator (NADS), built for NHTSA by TRW at the University of Iowa, is the most sophisticated driving simulator in the world. It is an operator-in-the-loop high fidelity driving simulator. The NADS motion system has nine degrees of freedom: a six degree-of-freedom hexapod supports the dome which contains the vehicle and visual system; two degrees of freedom for large horizontal excursions; and a full yaw rotational degree of freedom between the hexapod and dome. The visual system has a 360-degree field of view with sophisticated computer graphics capabilities. NADS will assist NHTSA, other federal agencies, and commercial organizations in enhancing human factors and crash avoidance research related to driver-vehicle-road interactions like driver impairment research, human factors research concerning driver workload and adaptation to emerging Intelligent Transportation System (ITS) equipment and technology, and to support regulations regarding automotive safety. A validated mathematical vehicle dynamics model and real-time simulation are prerequisites for performing this complicated task. VRTC's role is to develop and validate to a high degree of realism the vehicle dynamics computer simulation used within NADS. VRTC's staff is involved in the development of the vehicle handling models, the enhancement of the simulation code, and the validation of the simulation models via comparison with full-scale vehicle field experiments. VRTC is also responsible for developing parameter data sets representing the various vehicles that will be used on the NADS. VRTC has measured the parameters of a 1994 Ford Taurus and has developed a simulation model of the Taurus. Experimental testing and verification of the Taurus simulation model have been completed. Likewise, the parameters of a 1997 Jeep Cherokee and a 1998 Chevrolet Malibu have been measured, simulation models have been developed, and experimental testing and validation of these models have been performed. Additionally, measurements of the parameters of a Volvo tractor and Fruehauf semitrailer have been completed. A simulation model of this combination is currently under construction.

    NADS Publications By VRTC
    • Salaani, M.K., Heydinger, G.J, Grygier, P.A., "Closed Loop Steering System Model for the National Advanced Driving Simulator," March 2004, SAE Paper 2004-01-1072
    • Salaani, M.K., Heydinger, G.J, Grygier, P.A., "Experimental Steering Feel Performance Measures," March 2004, SAE Paper 2004-01-1074
    • Salaani, M.K., Heydinger, G.J, Grygier, P.A., “Heavy Tractor-Trailer Vehicle Dynamics Modeling for the National Advanced Driving Simulator,” SAE Paper 2003-01-0965.
    • Salaani, M.K., Heydinger, G.J, Grygier, P.A., “Evaluation of Heavy Tractor-Trailer Model used in the National Advanced Driving Simulator,” SAE Paper 2003-01-1324.
    • Salaani, M.K., Heydinger, G.J, Grygier, P.A., “Transport Delay Compensation for the Image Generator Used in the Natioanl Advanced Driving Simulator,” IMECE2003-42975, ASME International Mechanical Engineering Congress, November 15-21, 2003 Washington, D.C.
    • Salaani, M.K., Heydinger, G.J, Grygier, P.A., “Modeling and Implementation of Steering System Feedback for the National Advanced Driving Simulator,” SAE Paper 2002-01-1573.
    • Heydinger, G.J., Salaani, M.K., Grygier, P.A., “Vehicle Dynamics Modeling for the National Advanced Driving Simulator,” J. Automobile Engineering, Vol. 216, Part D, pp. 297-305.
    • Salaani, M. K., Heydinger, G. J., Grygier, P. A., “Parameter Determination and Vehicle Dynamics Modeling for the NADS of the 1998 Chevrolet Malibu,” March 2001, SAE Paper 2001-01-0140.
    • Salaani, M. K., Grygier, P. A., Heydinger, G. J., “Model Validation of the 1998 Chevrolet Malibu for the National Advanced Driving Simulator,” March 2001, SAE Paper 2001-01-0141.
    • Salaani, M. K., Heydinger, G. J. "Model Validation of the 1997 Jeep Cherokee for the National Advanced Driving Simulator," SAE Paper No. 2000-01-0700, March 2000.
    • Salaani, M. K., "Vehicle Dynamics Modeling for the National Advanced Driving Simulator of a 1997 Jeep Cherokee," SAE Paper No. 1999-01-0121, March 1999.
    • Chrstos, J. P. and Grygier, P. A., " Experimental Testing of a 1994 Ford Taurus for NADSdyna Validation," SAE Paper No. 970563, February 1997.
    • Chrstos, J. P. and Heydinger, G. J., "Evaluation of VDANL and VDM Road for Predicting the Vehicle Dynamics of a 1994 Ford Taurus," SAE Paper No. 970566, February 1997.
    • Garrott, W. R., Grygier, P. A., Chrstos, J. P., Heydinger, G. J., Salaani, M. K., Howe J. G., and Guenther, D. A., "Methodology for Validating the National Advanced Driving Simulator's Vehicle Dynamics (NADSdyna)," SAE Paper No. 970562, February 1997.
    • Howe, J. G., Rupp, G., Woodburn, C., Jang, B.C., Heydinger, G. J., and Guenther, D. A., "Improving Steering Feel for the National Advanced Driving Simulator," SAE Paper No. 970567, February 1997.
    • Salaani, M. K., Heydinger, G. J., "Powertrain and Brake Modeling of the 1994 Ford Taurus for the National Advanced Driving Simulator," SAE Paper No. 981190, February 1998. SAE Paper No. 970562, February 1997.
    • Salaani, M. K., Chrstos, J. P., and Guenther, D. A., "Parameter Measurement and Development of a NADSdyna Validation Data Set for a 1994 Ford Taurus," SAE Paper No. 970564, February 1997.
    • Salaani, M. K., Heydinger, G. J., and Guenther, D. A., "Validation Results from Using NADSdyna Vehicle Dynamics Simulation," SAE Paper No. 970565, February 1997.
    • Salaani, M. K., "Development and Validation of a Vehicle Model for the National Advanced Driving Simulator," Ph.D. Dissertation, The Ohio State University, June 1996.

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