New sensors needed to manufacture safer airbags are taking longer to perfect than expected, but automakers still face a 2003 federal deadline for phasing in the new equipment, according to a congressional report released June 13. The General Accounting Office (GAO) report said the primary challenge in meeting the advanced airbag rules issued last year was the development of reliable devices for determining the size of the occupant in the front seat. The new sensors should allow variations in the force of inflation so that occupants of different sizes are adequately protected without being subject to unnecessary and possibly lethal force. Although credited with saving nearly 7,000 lives, airbags have also been blamed for 175 deaths, mostly children and small women in relatively slow-speed crashes. The development of occupant-sensing technologies is taking longer than anticpated, according to the GAO. So far, the sensors have failed to demonstrate the ability to operate reliably over the presumed 15-year life of a vehicle. However, as of April 2000, no vehicle makers have reported they would fail to meet the Spet. 2003 deadline to place advanced devices in some vehicles, according to the GAO report. The report said National Highway Traffic Safety Administration officials planned to monitor the progress of sensor manufacturers to develop occupant-classification technology. Some vehicle makers already offer airbags that inflate with varying power depending on the force of a crash or whether the occupants are wearing their seat belts. But manufacturers believe full compliance with the advanced rules will require a sophisticated occupant sensor, the study said. The Alliance of Automobile Manufacturers said its safety experts were committed to meeting the timetable despite concern over performance of the sensors.