The debate over unintended acceleration, having lingered around the periphery of the auto industry for more than two decades, may be about to receive a fatal blow.
The National Highway Traffic Safety Administration (NHTSA) has proposed inclusion of a system that would shut down the throttle in the event that the brake and accelerator pedal were depressed simultaneously, and most automakers appear to be squarely behind it. Known as a brake-throttle override (BTO), the system would minimize the risk that drivers would lose control of their vehicles due to a stuck accelerator or entrapped floormat.
"We support the idea of making it standard," Wade Newton, a spokesman for the Alliance of Automobile Manufacturers, told Design News. "We've been behind it since it was first discussed in 2010." He said that the Alliance is now reviewing the proposal and will offer specific comments at a later date.
The Toyota Matrix was one of the vehicles that was recalled due to problems with unintended acceleration in 2010. (Source: Toyota)
The "unintended acceleration" debate goes back to the mid-1980s, when a class-action lawsuit was filed by a large group of Audi owners, stating that their vehicles experienced unexplained power surges. Audi argued that the surges were caused by drivers' misapplication of the pedals.
The debate was resurrected in 2009 and 2010, when some Toyota owners complained their vehicles accelerated unintentionally. In the Toyota case, however, a subsequent study by NHTSA revealed that there was no electronic cause for the phenomenon. The agency's conclusion was reached after hiring NASA engineers to examine the circuitry and comb through 280,000 lines of software code.
"We enlisted the best and the brightest engineers to study Toyota's electronics systems, and the verdict is in," US Transportation Secretary Raymond LaHood said in a 2011 news conference. "There is no electronic-based cause for unintended high-speed acceleration in Toyotas. Period."
Although the new proposal is still out for comment, auto industry experts said they expect the mandate to build atop the widespread availability of electronic throttle control (ETC) systems. ETC operates the throttle with a sensor and small electric motor, essentially eliminating the mechanical cable that would otherwise run from the accelerator to the throttle valve. Because such systems are essentially electronic, automakers could add the override capability with little or no additional hardware, simply by employing software that initiates a throttle cut-off if the accelerator is stuck and the brake is depressed.
It's not really the EGR valve, but it is part of the emissions controls system. After you romp on the gas, or after a long run on the highway the system will hold the idle high for a few seconds to help cool down the catalytic. Back in the days of carburetors there used to be a whole host of valves and solenoids to control coasting, so at least this part of the system has gotten a little simpler.
Actually, Charles, the culprit in this case was the EGR valve on a 1980 Buick Century. I've known more than one person who bypassed the thing when their cars got old enough to be able to avoid the annual inspections.
As a matter of fact, I have had a throttle control motor freeze on me, or at least, it stopped controlling and left me at a 70+ MPH "idle". I was able to control the car with the brakes, even though it was a "360" engine. The vehicle was a developmental one, and the control motor assembly was made by a company in Goshen, Indianna. The gearbox locking problem came from a case of pitch-line runout in the gear trains. If I could figure that out, why couldn't anybody else spot the problem?
Those cars did have regular ignition system switches so the racing engine could always be switched off. Nobody would have driven them if that had been under computer control.
The only safe electrical throttle controller that I have seen used a PWM driven solenoid to open the throttle valve, and if the power was switched off, the throttle would snap shut. The designers of that package even used redundant springs to assure that the throttle would close. So reloiable control is possible, but not cheap.
I like the idea of a kill switch. Last weekend my daughter rented a Toyota and the accelerator seem somewhat strange in that below 60 mph it seem to have somewhat of a mind of its own. At times, it felt was speeding up then all of a sudden slow down. Kind of a strange feeling.
William K: Although I'm sure you're joking about a twist-throttle, please note that motorcycles have had a handlebar-mounted engine kill-switch for longer than I've been riding (40-plus years). It's not a bad idea to add one to autos. I'm now teaching my teenager to drive, and I'd LOVE to have one!
As mentioned by others, this should not simply ask the computer to stop the engine, it should directly stop the ignition and/or the fuel feed. How well do you think the NHTSA-proposed system will work if the throttle-control motor becomes seized (yeah, that'll never happen), or if the computer gets a hair across its electronic tuchus?
Jack, I remember well what you've described here. I had a 1977 Olds Cutlass with the same problem. The problem was the catalytic converter in its early years. Until the vehicle was warmed up, it would balk whenever I stepped on the accelerator. It made for some very exciting turns into oncoming traffic.
I sure hope you are right that there is a method of turning it off. There are times during maintenance when I will intentionally have one foot on the accelerator and another on the brake. In addition, years ago my parents' car (1980 Buick Century) had some problem where the engine would die if you didn't keep giving it gas. When you stopped at an intersection, you had to keep giving it gas. (The problem was finally determined to be caused by a failure with some useless government mandated equipment on the car.)
THis relates to the comment about the big red emergency stop buttons on machines: not only are they a dedicated stop system, but in addition, for all of my controls engineering career, there was a rule that they had to work in spite of any failure of the controls logic. To clarify that, it means that the stop function must have priority above all other functions. OF course, that can be quite inconvenient and even messy, which is why most machines also have "stop" buttons that are not "emergency stop" buttons. MOst of those machines are much less dangerous than cars, so why not assure that there is a means available to shut off a car?
On the other hand, for those drivers unable to differentiate between an accelerator pedal and a brake pedal, perhaps they could be fitted with a twist-grip throttle like a motorcycle has. That might help them remember the difference. Of course, the most effective method would be to remove their driving privaleges permanently the first time that mistake results in an accident. That penalty could help folks pay closer attention to what theyare doing while at the wheel.
Regarding the effect of BTO on race driving, Toyota has sent us this: "If the brake is pressed first, followed by the accel pedal, BTO does not engage. This allows for hill starts...Also, for those double-footed drivers, BTO won't engage because the system can differentiate between intentional accel pedal input and a stuck pedal. If the APPS detects accel pedal movement, it assumes the pedal is not stuck and the driver is intentionally pressing both pedals."
Tesla Motors plans to roll out a “compelling, affordable electric car” that will sell for about half the price of its high-profile Model S by the end of 2016, company chairman Elon Musk said last week.
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