US Department of Transportation National Highway Traffic Safety Administration DOT HS 809 297 July 2001 An Evaluation of Existing Tire Pressure Monitoring Systems This publication is distributed by the U.S. Department of Transportation, National Highway Traffic Safety Administration, in the interest of information exchange. The opinions, findings, and conclusions expressed in this publication are those of the author(s) and not necessarily those of the Department of Transportation or the National Highway Traffic Safety Administration. The United States Government assumes no liability for its contents or use thereof. If trade or manufacturers= names or products are mentioned, it is because they are considered essential to the object of the publication and should not be construed as an endorsement. The United States Government does not endorse products or manufacturers. Technical Report Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient's Catalog No. DOT 809 297 4. Title and Subtitle 5. Report Date An Evaluation of Existing Tire Pressure Monitoring Systems July 2001 6. Author(s) 7. Performing Organization Code Paul Grygier, W. Riley Garrott, and Elizabeth N. Mazzae, National Highway Traffic Safety Administration 8. Performing Organization Report No. James D. MacIsaac Jr., Richard L. Hoover, Devin Elsasser, and Thomas A. Ranney, - Transportation Research Center (TRC) Inc. 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) National Highway Traffic Safety Administration Vehicle Research and Test Center 11. Contract or Grant No. P.O. Box B-37 East Liberty, OH 43319-0337 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered National Highway Traffic Safety Administration Technical report 400 Seventh Street, S.W. 14. Sponsoring Agency Code Washington, D.C. 20590 NHTSA/NRD-50 15. Supplementary Notes The authors acknowledge the support of this effort by: Larry Armstrong, Scott Baldwin, David Dashner, Lyle Heberling, Larry Jolliff, Ed Parmer, Leslie Portwood, Jim Preston, Greg Stevens, and Tim Van Buskirk of TRC. 16. Abstract In the TREAD Act of November 1, 2000, Congress required the National Highway Traffic Safety Administration (NHTSA) to develop a rule requiring all new light vehicles to be equipped with a warning system to indicate to the operator when a tire is significantly underinflated. In response to this requirement, NHTSA undertook an evaluation of existing OEM and aftermarket tire pressure monitoring systems. In this evaluation NHTSA determined the capabilities of existing technologies and the methods of warning the driver that were under consideration by system manufacturers. Based on this evaluation, NHTSA will determine the minimum system performance criteria that are technically feasible and provide the most useful information to the driver for preventing unsafe conditions. Through its testing, NHTSA found that systems that use sensors to directly measure tire pressure (pressure-sensor based systems) were better able to detect underinflation, had more consistent warning thresholds, and were quicker to provide underinflation warnings than the systems that infer tire pressure from monitoring wheel speeds (wheel-speed based systems). Training the systems presented at least some level of problem for both system types. Wheel-speed based systems were found to be easier to maintain since there are no battery life concerns and the fact that sensors are not exposed to tire mounting and roadway hazards. An examination of driver interfaces for existing TPMS showed significant variation in methods of visual warning presentation. Visual displays were frequently difficult to see or comprehend, or both. The variation in visual warning presentation demonstrated the need for standardization of the visual warnings of tire underinflation to avoid driver confusion. Icon comprehension testing, which examined the ability of two ISO icons and 13 alternative icons to communicate the message of low tire pressure, showed that the ISO icons performed worse than all of the other icons. Six of the alternative icons received 100 percent comprehension. One of the icons was identified as most likely to be successful as an indicator of significant underinflation. 17. Key Words 18. Distribution Statement tire pressure, tire pressure monitoring, TPMS, underinflation, Document is available to the public from TREAD Act. the National Technical Information Service Springfield, VA 22161 19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price Unclassified Unclassified Form DOT F 1700.7 (8-72) Reproduction of completed page authorized CONVERSION FACTORS Approximate Conversions to Metric Measures Approximate Conversions to English Measures Symbol When You Know Multiply by To Find Symbol Symbol When You Know Multiply by To Find Symbol LENGTH LENGTH in inches 2.54 centimeters cm mm millimeters 0.04 inches in ft feet 30 centimeters cm cm centimeters 0.4 inches in mi miles 1.6 kilometers km m meters 3.3 feet ft km kilometers 0.6 miles mi AREA AREA in2 square inches 6.5 square centimeters cm2 ft2 square feet 0.09 square meters m2 cm2 square centimeters 0.16 square inches in2 mi2 square miles 2.6 square kilometers km2 km2 square kilometers 0.4 square miles mi2 MASS (weight) MASS (weight) iv oz ounces 28 grams g g grams 0.035 ounces oz lb pounds 0.45 kilograms kg kg kilograms 2.2 pounds lb PRESSURE PRESSURE psi pounds per inch2 0.07 bar bar bar bar 14.50 pounds per inch2 psi psi pounds per inch2 6.89 kilopascals kPa kPa kilopascals 0.145 pounds per inch2 psi VELOCITY VELOCITY mph miles per hour 1.61 kilometers per hour km/h km/h kilometers per hour 0.62 miles per hour mph ACCELERATION ACCELERATION ft/s2 feet per second2 0.30 meters per second2 m/s2 m/s2 meters per second2 3.28 feet per second2 ft/s2 TEMPERATURE (exact) TEMPERATURE (exact) °F Fahrenheit 5/9 (Celsius) - 32°C Celsius °C °C Celsius 9/5 (Celsius) + 32°F Fahrenheit °F TABLE OF CONTENTS TABLE OF CONTENTS ...........................................................................................................V LIST OF APPENDICES .......................................................................................................... XI LIST OF FIGURES .................................................................................................................XII LIST OF TABLES ................................................................................................................. XIV EXECUTIVE SUMMARY ................................................................................................... XVI 1.0 INTRODUCTION............................................................................................................1 2.0 OBJECTIVES ..................................................................................................................2 3.0 SYSTEMS TESTED ........................................................................................................5 3.1 SUMMARY OF TPMS/VEHICLES TESTED.........................................................................5 3.1.1 Description of the Wheel-Speed Based TPMS Evaluated......................................6 3.1.1.1 System A............................................................................................................7 3.1.1.2 System B ............................................................................................................8 3.1.1.3 System C ..........................................................................................................10 3.1.1.4 System D..........................................................................................................12 3.1.2 Description of the Pressure-Sensor Based TPMS Evaluated ..............................13 3.1.2.1 System E ..........................................................................................................14 3.1.2.2 System F...........................................................................................................16 3.1.2.3 System G..........................................................................................................17 3.1.2.4 System H..........................................................................................................18 3.1.2.5 System I ...........................................................................................................20 3.1.2.6 System J ...........................................................................................................22 3.2 WHEEL-SPEED BASED TIRE PRESSURE MONITORING SYSTEM SPECIFICATIONS ...........24 3.3 PRESSURE-SENSOR BASED TIRE PRESSURE MONITORING SYSTEM SPECIFICATIONS ....24 v 3.3.1 Cost ......................................................................................................................24 3.3.2 Cold Inflation Pressure Ranges...........................................................................26 3.3.3 Mini-spare Tires ..................................................................................................26 3.3.4 Warning Thresholds.............................................................................................26 3.3.5 Temperature Ranges ............................................................................................28 3.3.6 Specified Pressure Accuracies.............................................................................29 4.0 INSTRUMENTATION .................................................................................................30