The release of a rule by the U.S. National Highway Traffic Safety Administration (NHTSA) has put tire monitoring systems one step closer to becoming mandatory on U.S. vehicles. In response to a mandate in the Transportation Recall Enhancement, Accountability, and Documentation (TREAD) Act of 2000, NHTSA issued part one of a two-part final rule requiring tire pressure monitoring systems (TPMSs) that warn the driver when a tire is significantly under-inflated. “Properly maintained, properly inflated tires are crucial for safety,” said Jeffrey W. Runge, M.D., NHTSA administrator. “This new standard, and our continuing studies of its implementation, will help Americans keep their tires in peak condition for optimum control and braking.” According to a NHTSA research survey, 27 percent of passenger cars on U.S. roadways are driven with one or more substantially under-inflated tires. In addition, the survey found that 33 percent of light trucks (including sport utility vehicles, vans and pickup trucks) are driven with one or more substantially under-inflated tires. Operating a vehicle with substantially under-inflated tires can result in a tire failure, such as instances of tire separation and blowouts, with the potential for a loss of control of the vehicle. Under-inflated tires also shorten tire life and increase fuel consumption. The new Federal Motor Vehicle Safety Standard applies to passenger cars, trucks, multipurpose passenger vehicles, and buses with a gross vehicle weight rating of 10,000 pounds or less, except those vehicles with dual wheels on an axle. This document establishes two compliance options for the period between Nov. 1, 2003, and Oct. 31, 2006. These options are designed to allow vehicle manufacturers to use either of the two types of TPMS currently available — one of which measures the pressure in each tire, and another which uses a vehicle’s antilock brake system hardware to sense tire pressure differences by monitoring the speed of tire revolution. The second part of this final rule will be issued by March 1, 2005, and will establish performance requirements that will become effective on Nov. 1, 2006. In the meantime, the agency will leave the rulemaking docket open for the submission of new data and analyses concerning the performance of TPMSs, including both the systems in the field as well as systems under development. NHTSA urges those commenting to substantiate their comments with data and information to the maximum extent possible. The agency also will conduct a study comparing the tire pressures of vehicles with no TPMS to the pressures of vehicles with the different systems. The study will give the agency additional information regarding the extent to which these vehicles have tire pressures closer to the vehicle manufacturer’s recommended inflation pressure than vehicles without a TPMS, and also regarding the extent to which these vehicles have fewer significantly under- inflated tires. This will help NHTSA make a decision on the second part of the rule.