A federal appeals court on August 6 ordered the National Highway Traffic Safety Administration (NHTSA) to rewrite a regulation that will require low tire pressure warning devices on new cars. The 2nd U.S. Circuit Court of Appeals in NY called NHTSA’s tire-warning rule “arbitrary and capricious” and contrary to Congress’s intent in passing a tire safety law. NHTSA’s intent was to give automakers two ways to comply with the mandate: using “direct” systems that warn drivers of a loss of pressure in any tire, or cheaper “indirect” systems that use anti-lock brake technology to warn the driver if one wheel spins faster than another. Attorneys for Public Citizen, the Center for Auto Safety and the New York Public Interest Research Group argued that the indirect systems were ineffective, since there would be no warning if two tires on the same axle were underinflated, or if all four of a vehicle’s tires were underinflated.The court agreed with the safety groups’ arguments and ordered NHTSA to rewrite the legislation. The indirect system was supported by automakers because it would cost roughly half of the cost of a direct system. The direct system requires a sensor inside each tire, and triggers a warning if the pressure falls below the recommended limit.