V.  Summary of Preliminary Determination About the Final Rule


    In this section, NHTSA summarizes its preliminary determination about the final rule that was submitted to OMB in December 2001.


    A.   Alternative Long-Term Requirements Analyzed in Making Preliminary Determination

    For purposes of the preliminary determination, the agency analyzed three alternatives. The first alternative (four tires, 20 percent) would have required a vehicle's TPMS to warn the driver when the pressure in any single tire or in each tire in any combination of tires, up to a total of four tires, fell to 20 percent or more below the placard pressure, or a minimum level of pressure specified in the standard, whichever pressure was higher. The second alternative (three tires, 25 percent) would have required a vehicle's TPMS to warn the driver when the pressure in any single tire or in each tire in any combination of tires, up to a total of three tires, fell to 25 percent or more below the placard pressure, or a minimum level of pressure specified in the standard, whichever pressure was higher. The third alternative (four tires, 25 percent) combined aspects of the first two alternatives. It would have required a vehicle's TPMS to warn the driver when the pressure in any single tire or in each tire in any combination of tires, up to a total of four tires, fell to 25 percent or more below the placard pressure, or a minimum level of pressure specified in the standard, whichever pressure was higher. The minimum levels of pressure specified in the standard would have been the same for all three alternatives.

    The agency estimated that the four-tire, 20 percent alternative would have prevented from 141 to 145 fatalities and prevented or reduced in severity from 10,271 to 10,611 injuries per year. (30) The agency estimated that the average net cost of this alternative would have been from $76.77 to $77.53 per vehicle. (31) Since approximately 16 million vehicles are produced for sale in the United States each year, the total annual net cost of this alternative would have been from $1.228 billion to $1.241 billion. The net cost per equivalent life saved would have been from $5.1 million to $5.3 million.

    The agency estimated that the three-tire, 25 percent alternative would have prevented 110 fatalities and prevented or reduced in severity 7,526 injuries per year. The agency estimated that the average net cost would have been $63.64 per vehicle, and the total annual net cost would have been $1.018 billion. The net cost per equivalent life saved would have been $5.8 million.

    The agency estimated that the four-tire, 25 percent alternative would have prevented 124 fatalities and prevented or reduced in severity 8,722 injuries per year. The agency estimated that the average net cost would have been $53.87 per vehicle, and the total annual net cost would have been $862 million. The net cost per equivalent life saved would have been $4.3 million.

    The agency noted that the vehicle costs of these alternatives could be reduced in the future as manufacturers learned how to produce TPMSs more efficiently. Moreover, maintenance costs could be significantly reduced in the future if manufacturers could mass produce a direct TPMS that did not require the pressure sensors to be replaced when the batteries are depleted. (32)

    NHTSA considered these three alternatives because the agency believed that TPMSs that complied with these alternatives would warn drivers of significantly under-inflated tires in a wide variety of reasonably foreseeable circumstances, including when more than one tire was significantly under-inflated. The agency also believed that improved indirect TPMSs could be developed to meet the requirements of the three-tire, 25 percent alternative and hybrid TPMSs could be developed to meet the three-tire, 25 percent and four-tire, 25 percent alternatives. Thus, the agency believed that these alternatives would provide an effective warning while striking a reasonable balance between encouraging further improvements in TPMS technology and stringency of the performance requirements and striking a reasonable balance between safety benefits and costs.


    B. Phase-In and Long-Term Requirements

    To facilitate compliance, the preliminary determination specified a four-year phase-in schedule, (33) During the phase-in, i.e., between November 1, 2003 and October 31, 2006, it would have allowed compliance with either of two options: a four-tire, 25 percent option or a one-tire, 30 percent option. Under the first option, a vehicle's TPMS would have had to warn the driver when the pressure in one or more of the vehicle's tires, up to a total of four tires, was 25 percent or more below the placard pressure, or a minimum level of pressure specified in the standard, whichever pressure was higher. Under the second option, a vehicle's TPMS would have had to warn the driver when the pressure in any one of the vehicle's tires was 30 percent or more below the placard pressure, or a minimum level of pressure specified in the standard, whichever pressure was higher. The minimum levels of pressure specified in the standard were the same for both compliance options.

    Under both options, the preliminary determination would have required the low tire pressure warning telltale to remain illuminated as long as any one of the vehicle's tires remained significantly under-inflated, and the key locking system was in the ""On"" (""Run"") position. The telltale could have been deactivated automatically only when all of the vehicle's tires ceased to be significantly under-inflated, or manually in accordance with the vehicle manufacturer's instructions.

    The preliminary determination would have required each TPMS to be compatible with all replacement or optional tires (but not rims) of the size(s) recommended for use on the vehicle by the vehicle manufacturer. It would also have required that the telltale perform a bulb-check at vehicle start-up. It specified written instructions explaining the purpose of the low tire pressure warning telltale, the potential consequences of significantly under-inflated tires, the meaning of the telltale when it was illuminated, and what actions drivers should take when the telltale is illuminated, to be placed in the vehicle's owner's manual.

    The preliminary determination would not have required TPMSs to monitor the spare tire, either when the tire was stowed or when it was installed on the vehicle. It also would not have required the TPMS to indicate a system malfunction.

    The agency created the one-tire, 30 percent option so that vehicle manufacturers could continue to install current indirect TPMSs for several more years, thus providing additional time and flexibility for innovation and technological development. The agency created the other option by adjusting the definition of ""significantly under-inflated"" for the four-tire option to 25 percent (instead of 20 percent) so that improved indirect TPMSs and hybrid TPMSs could be used to comply with the TPMS standard. After the phase-in, i.e., after October 31, 2006, the second option would have been terminated, and the provisions of the first option would have become mandatory for all new vehicles.

    The agency tentatively believed that a four-tire, 25 percent requirement was preferable for the long-term because it would require TPMSs that warn drivers about all combinations of significantly under-inflated tires and provide more timely and effective warnings. The agency tentatively believed that a one-tire, 30 percent requirement would allow TPMSs that do not warn about all combinations of significantly under-inflated tires and do not provide warnings until the extent of under-inflation reaches 30 percent below the placard pressure. Thus, it appeared that a four-tire, 25 percent requirement would better fulfill the purposes of the TPMS mandate in the TREAD Act, while encouraging further improvements in TPMS technology.




    30 NHTSA assumed that drivers would respond differently to different information displays. To get the upper bound, the agency assumed that manufacturers that installed direct TPMSs would also install a display showing the pressure of each tire. Currently only direct TPMSs are capable of displaying individual tire pressure. The agency also assumed that 33 percent of drivers would respond to such a display by re-inflating their tires when they became under-inflated by 10 percent, and that the other 67 percent would respond by re-inflating their tires when they became under-inflated by 20 percent, i.e., when the warning telltale would have been activated. To get the lower bound, the agency assumed that manufacturers would install only a low tire pressure warning telltale, as would have been required. Thus, all drivers would not re-inflate their tires until they became under-inflated by 20 percent, and the warning telltale was activated.

    31 The net cost is the vehicle cost plus the maintenance cost minus the fuel and tread wear savings. The difference in costs is due to the cost of adding an individual tire pressure display. The agency assumed that manufacturers would install direct TPMSs on vehicles that are not equipped with ABS because the cost of adding a direct TPMS was significantly less than the cost of adding ABS and an indirect TPMS.

    32 One TPMS manufacturer, IQ-mobil Electronics of Germany, indicated in its comments that it has developed a pressure sensor that does not require a battery.

    33 The phase-in schedule was as follows: 10 percent of a manufacturer's affected vehicles would have had to comply with either compliance option in the first year; 35 percent in the second year; and 65 percent in the third year. In the fourth year, 100 percent of a manufacturer's affected vehicles would have had to comply with the long-term requirements, i.e., the four-tire, 25 percent compliance option.