The measures amend Federal Motor Vehicle Safety Standard 138, Tire Pressure Monitoring Systems (Reference File, 901: 1921) and grant some of the 17 petitions the agency received in response to the April final rule (33 PSLR 390, 4/11/05) .

The decision to not require that tire pressure monitors work with replacement and spare tires has been a sticking point for the consumer advocacy group Public Citizen and a tire pressure monitor manufacturer.

The standard also requires automakers to certify vehicle compliance with the tires installed on the vehicle at the time of initial sale of the vehicle. TPMSs must have a low-pressure warning telltale that must remain illuminated the entire time a tire remains significantly underinflated as well as a telltale that indicates a TPM system malfunction within 20 minutes of the malfunction.

The agency said the original final rule sought to ease implementation of the requirements by allowing vehicle manufacturers to earn carry-forward credits for compliant vehicles produced in excess of the phase-in requirements and carry-backward credits to allow automakers to defer compliance under certain conditions.

A petitioner to the final rule--a manufacturer of tire pressure monitors, ETV Corp. Pty Ltd.--challenged the agency's decision, noting that the original intent of the rule grew out of the Transportation Recall Enhancement, Accountability, and Documentation Act. The decision to not require spares and replacements to be monitored would directly contradict the intention of the TREAD Act, which stated that tire pressure monitors must warn a driver when a tire is significantly underinflated, ETV noted.

The petitioner said spares should be covered under the rule. The company reasoned that when a spare is placed on a vehicle, it would illuminate the malfunction indicator lamp, thereby masking other tire or system faults.

The petitioner therefore recommended that the standard be amended to require that spares be fitted with a TPMS sensor so tire pressure monitors would continue to function in compliance with the standard.

Similarly, Public Citizen attorney Laura MacCleery told BNA that the consumer group has had long-term concerns that replacement tires will not be covered by the standard.

The group originally submitted comments to the agency's September 2004 proposal. After the TPMS rulemaking became final in April, Public Citizen submitted a petition for reconsideration reiterating its concerns over various "weak" provisions of the rule. The group withdrew the petition, opting instead to file suit with tire manufacturers against the U.S. government. The groups challenged, among other things, the agency's decision to not require TPMSs to operate with replacement tires (33 PSLR 580, 6/13/05). The plaintiffs said the rule was weak and called the replacement tire exemption a "dangerous omission" -- particularly considering that an estimated 61 percent of passenger-car and 54 percent of light-truck mileage occurs on replacement tires.

The agency said it based its decision to not cover replacement tires on several factors. It reasoned that drivers are aware that temporary tires are not intended for extended use; spares pose operational problems for both direct and indirect TPMSs; there is a disincentive for automakers to supply a full-size spare or any spare at all, if TPMS compliance were required; and there would be increased costs to manufacturers with little, if any safety gains, if a spare tire must be monitored.

"The agency is basically willing to let people live with systems that are not required to work after the first generation of tires that come on the vehicle as original equipment," MacCleery said. "The agency's view is that the effect of this is going to be minimal."

MacCleery added, "Vehicle manufacturers didn't want the headache of certifying their tires to work with replacement tires. They didn't want to have to test the systems to see how the tires fared with the monitor systems, so NHTSA exempted replacement tires. The agency believes most tires will comply anyway because they should work the same, but then why exempt them?"

She said there is no reason manufacturers cannot make TPMSs work with replacement tires and to certify those tires to TPMS requirements. "For the few outlier tires that can't comply, then you exempt them," she said. "You shouldn't gut the rule and carve a place for outliers."

Public Citizen's MacCleery said some consumer groups and tire manufacturers objected to the methodology the agency uses to determine underinflation. The rule requires TPMSs to alert drivers if any tire falls 25 percent below the recommended inflation pressure. A key problem with that, Public Citizen in its suit against NHTSA say, is that the baseline by which the 25 percent is measured is dictated by the recommended tire pressure set by automakers, not by the tire manufacturers. "From the tire maker's perspective, by the time the alarm goes off the tire could be outside its real margin of safety. In a hybrid tire pressure monitor system, consumers won't even know for 20 minutes," MacCleery said.

Other key points of the final rule amending FMVSS 138 includes:

Postponing the compliance date for the standard's required TPMS-related owner's manual statement until Sept. 1, 2006 (model year 2007). This measure grants petitions' request for additional lead time to incorporate the required language into the vehicle owner's manual. The agency said it does not believe that extending the compliance date in this manner (consistent with a recommendation in one of the petitions) would result in any safety consequences. And delay of the owner's manual requirements would not impact the functioning of the TPMS or the warnings that it provides, it added.

Retaining the final rule's requirement for the TPMS malfunction indicator lamp to illuminate whenever there is a malfunction that affects the generation of transmission of control or response signals in the monitoring system. But, yielding to petitioners, the agency said it decided to amend the standard's test procedures for malfunction detection to clarify that telltale lamps are not to be disconnected because such malfunctions will be indicated during the bulb check(s) required under the standard.

Modifying tests to reduce the pressure adjustment (below the TPMS activation threshold) from the current 2 pounds per square inch (psi) to 1 psi. The 2-psi adjustment was intended to facilitate testing, but several petitioners expressed concern that a 2-psi adjustment could allow TPMSs to achieve compliance with an underinflation detection capability of 30 percent or more. The agency said it expects that a 1-psi adjustment would continue to facilitate testing while maintaining the underinflation level close to the standard's 25 percent underinflation activation threshold.

Modifying the Reporting Requirements to differentiate the reports to be submitted to the agency for each of the two phase-in periods. NHTSA said this change more clearly differentiates between the TPMS standard's two phase-in production periods, which are of different lengths (almost 11 months vs. one year).

Petitions for reconsideration for this rule, due Oct. 24, should refer to Docket 2005-22251 and be submitted to Administrator, Room 5220, National Highway Traffic Safety Administration, 400 Seventh Street, S.W., Washington, D.C. 20590.

Additional information is available by contacting George Soodoo or Samuel Daniel, Office of Crash Avoidance Standards, at (202) 366-2720, for nonlegal issues and Eric Stas, Office of Chief Counsel, at (202) 366-2992, for legal issues.