STERLING HEIGHTS, MI – When Washington proposes its final rule mandating tire pressure monitoring in 2006, expect a pair of technologies to proliferate, not just one, says a TRW Automotive executive.

Philip Cunningham, TRW Automotive product planning director-chassis products, says indirect systems – so called because they rely on ancillary factors such as wheel speed to detect pressure loss – are adequate for passenger cars.

Tire pressure monitoring (TPM) systems will be required as of Nov. 1 of this year.

Direct systems actually measure tire pressure by employing a sensor at each wheel. And Cunningham suggests light trucks, such as SUVs, demand the precise readings this technology affords because the stakes are higher – especially when the vehicles are operated in a loaded condition.

TRW reveals it will supply direct tire pressure-monitoring (TPM) technology for General Motors Corp.’s next-generation SUVs and pickups. Known as the “Entire Solution,” it is being developed in partnership with Michelin SA.

“This will be one of the first high-volume applications of our direct tire-pressure-monitoring technology,” TRW Automotive President and CEO John Plant says.

In the wake of the Firestone fiasco, which saw tire failure linked to underinflation, national attention was focused on the issue of maintaining proper tire pressure. The National Highway Traffic Safety Admin. announced it favored direct systems – the more expensive of the two technologies.

But the Office of Management and Budget quashed NHTSA’s proposal. Instead, it endorsed indirect technology which – because it commonly piggybacks on antilock brake system sensors – is less costly, but also less precise.

NHTSA declared it would study both technologies between Nov. 1, 2003 – after which TPM systems must be featured on all new vehicles – and Oct. 31, 2006. Then NHTSA will issue a final rule that is expected to set a performance standard.

Cunningham predicts auto makers will be allowed to use whichever technology allows them to meet the standard, a freedom the industry has endorsed (see related story: Continental-Teves Applauds TPMS Action).

But extending choice to auto makers irked independent safety advocates such as Public Citizen. The nonprofit organization filed suit against Transportation Secretary Norman Y. Mineta, claiming Washington’s support for indirect systems “put cost ahead of safety.”

The cost benefits of indirect TPM systems could be short-lived, predicts Alain Charlois, TRW product planning director-occupant safety systems. Charlois tells Ward's the receiver used to monitor frequencies emitted by a direct system’s individual tire sensors could be used to support features such as keyless entry.

In addition, advances in miniaturization could see sensors built into a tire’s rubber, which also portends benefits for data tracking as required by the Transportation Recall Enhancement Accountability and Documentation (TREAD) Act.