Sudden Unintended Acceleration:
The Cherokee Story
One car races backward out of an airport parking space... another lurches out of a carwash stall at high speed...
These were not displays of reckless driving, but the real-world consequences of reckless auto design that continues to cause scores of injuries and hundreds of collisions. Auto makers and federal safety regulators have known about the problem of sudden unintended acceleration (SUA) at least since the 1980s, when more than 1,000 such incidents were reported involving Audi's.
During the 1980s, the National Highway Traffic Safety Administration (NHTSA) also received complaints of similar problems with Nissan 280/300ZX models and Maxima, the Acura Legend, the Honda Accord, and various Ford and General Motors models. NHTSA opened several defect investigations but, for the most part, closed them without finding a "defect trend," instead concluding that the accelerations were caused by "driver error" or "pedal misapplication." Despite the accumulating evidence, when the Center for Auto Safety asked NHTSA in 1990 to investigate sudden acceleration problems, the agency declined.
Audi eventually did recall its cars to retrofit them with gear-shift interlocks, which require that drivers apply the brakes before shifting out of the "park" position. Nissan did the same for its 1979-1987 280/300 ZXs, but some auto makers continue to insist the problem isn't serious and even, in some instances, that it doesn't exist.
The Cherokee Story
Chrysler, the target of the most recent surge of complaints, still says the unintended accelerations are caused by driving -- not design -- errors, even though in 1991 the auto maker voluntarily recalled 1989 and 1990 model 6-cylinder Cherokees to replace a throttle position sensor (TPS) that it acknowledged was causing "intermittent high idle" after the engine was started. 1996 was pivotal in the long story of delay in addressing Chrysler's sudden acceleration problems. By then, NHTSA had received more than 400 complaints about Jeep Cherokees accelerating without warning. (The agency now has more than 570 such reports involving Cherokees and Grand Cherokees.)
By the mid-1990s, even the International Carwash Association (ICA) knew about the problem: it issued a "special alert" to warn its members that carwash operators were experiencing unexpected "lurching" when Cherokees exited the wash. According to the ICA alert, when the cars were shifted into gear, they unexpectedly accelerated even though the gas pedal was not depressed. In at least one incident, when the driver was extricated from a 1996 Cherokee after it had suddenly accelerated out of a carwash, bystanders had to turn off the ignition to stop the rear wheels from spinning. In April of 1996, the Center for Auto Safety again asked NHTSA to investigate, citing the ICA alert and 12 complaints involving 1991-1995 model Cherokees. Again, NHTSA declined to open a defect investigation, but it did start a "pre-investigative file" and surveyed 88 owners of 1993 Cherokees who had reported experiencing sudden acceleration in an attempt to find similarities that would help identify the source of the problem.
Chrysler Blames Drivers
As the number of complaints rose, the media began reporting on incidents of sudden acceleration. Chrysler responded by denying the problem exists, blaming instead "pedal misapplication" by drivers who were either not familiar with their vehicles or seated incorrectly behind the wheel. Chrysler said eyewitnesses who did not report seeing brake lights come on during the accelerations was evidence that the drivers were in fact stepping on the accelerator, not the brake pedal. Even NHTSA joined Chrysler in arguing that such accidental accelerations were fairly common, that they were caused by driver error, and that there was no scientific evidence that they occurred independent of drivers' errors.
Chrysler went a step further: it performed a "test" which it claimed proved that sudden accelerations were simply the result of drivers stepping on the accelerator instead of the brake. This test consisted of a company engineer simultaneously depressing the accelerator and brake of a Grand Cherokee, both while parked and while in motion, to show that the brakes were more powerful than the engine. That test, however, did not reflect the real-world events in which vehicles suddenly lurch into gear at high speed.
One Case Among the Many
Policewoman Carmen Rodriguez was on her daily rounds patrolling a parking area at Miami International Airport when she was struck by a Jeep Grand Cherokee backing out of a parking space. The Jeep's undercarriage caught the back of her belt and she was dragged, face down, 150 feet as the car accelerated. The driver later said that as she shifted from park to reverse, she thought her foot was on the brake when in fact it was on the accelerator. After extensive litigation, Chrysler settled with the victim.
A Dangerous Position
Far from proving Chrysler's argument that driver error was to blame, the Rodriguez case demonstrated that the fault, in this instance, was with design decisions: the positioning of the brake pedal and the lack of a gear-shift interlock that would make it impossible to shift out of "park" unless the brake pedal were depressed.
In a nationally televised broadcast, an engineering firm hired by the ABC News Primetime Live reported that the pedals in the Cherokee were positioned in the same location as those in the Audi's that had experienced high rates of sudden acceleration during the 1980s. The engineers concluded that pedal misapplication was "design induced" because Chrysler had placed the brake pedal too far to the left, leaving inexperienced drivers unaware that they were depressing the accelerator. Chrysler confirms this finding during the same ABC News interview. In 1994, Chrysler moved the brake pedal 15 millimeters to the right.
Shortly before the Primetime Live broadcast, Chrysler announced it would mount a "service campaign" to retrofit pre-1996 Jeep Cherokees with gear-shift interlocks. (Beginning in 1996, such interlocks became standard in Cherokees and Grand Cherokees. The device has been standard in many vehicles since the early 1990s.) The service campaign did more than blunt the media criticism, it preempted action by the NHTSA.
What Did Chrysler Know, and When?
Chrysler received reports of sudden acceleration as early as 1988. Internal documents and meeting notes indicate that, despite claims to the contrary, the company was reluctant to design and install a gear-shift interlock unless it was compelled to do so by government regulators or competitive pressures.
In an Oct. 4, 1996, letter to the Office of Defects Investigation, the auto maker disclosed that it knew of 98 incidents of unintended acceleration between 1993 and 1996 involving Cherokees, and another 241 involving Grand Cherokees. NHTSA's analysis found that complaints about sudden acceleration by 1993-1995 model Cherokees and Grand Cherokees were coming in at more than four times the rate for the next closest similar vehicle.
Multiple Causes
The number and variety of complaints received by NHTSA suggest that more than one cause is contributing to sudden accelerations in motor vehicles. Reports allege:
- Cruise control failure.
- High idling speeds.
- Intermittent unintended acceleration when shifting into gear.
- Failure of the throttle position sensor (both before and after Chrysler's 1991 recall to replace the sensor), causing both high idling speed and unintended acceleration.
- Failure of the electronic control module.
- Failure of the throttle cable or other hardware.
- Most complaints state that the engine idled too fast or that the engine raced uncontrollably and the brakes could not overpower it.
Conclusion
Correcting the problems that turn cars and sports utility vehicles into high-speed unguided missiles has been slow -- and typically induced by consumer pressures and litigation. In this instance at least, it is clear that federal regulators have chosen to follow rather than lead efforts to correct those problems.
