NHTSA says ABS not as cool as they thought

http://www.thetruthaboutcars.com/nhtsa-abs-braking-increases-fatal-run-off-road-crashes-by-34/

*NHTSA: ABS Braking Increases “Fatal Run-off-Road Crashes” by 34%

By Robert Farago October 22, 2009

A National Highway Transportation Safety Administration (NHTSA) study on Antilock Braking Systems (ABS) reveals that they’re not all that. In fact, the technology increases fatalities in certain circumstances. (Not that Frank Williams didn’t warn you back in 2006.) “ABS has close to a zero net effect on fatal crash involvements. Fatal run-off-road crashes of passenger cars increased by a statistically significant 9 percent (90% confidence bounds: 3% to 15% increase), offset by a significant 13-percent reduction in fatal collisions with pedestrians (confidence bounds: 5% to 20%) and a significant 12-percent reduction in collisions with other vehicles on wet roads (confidence bounds: 3% to 20%).,” “The Long-Term Effect of ABS in Passenger Cars and LTVs” reports [download pdf here]. “ABS is quite effective in nonfatal crashes, reducing the overall crash- involvement rate by 6 percent in passenger cars (confidence bounds: 4% to 8%) and by 8 percent in LTVs (confidence bounds: 3% to 11%).” That doesn’t sound . . . confidence inspiring. In fact, that nine percent increase looks even worse close up. A LOT worse.

From page 8:

But previous statistical evaluations of ABS have had ambiguous results. Analyses of data from the early 1990s showed significant increases in fatal run-off-road crashes with ABS, on the order of 28 percent. The increase was baffling, given the success of ABS on the test track. However, at that time, many drivers did not yet know how to use ABS correctly. During the mid-1990s, the safety community worked hard to inform the public about the correct use of ABS (“Don’t let up on the brakes”; “Stomp, stay, and steer”). A second generation of analyses circa 2000 showed much smaller increases in run-off-road crashes that were no longer statistically significant. But they were based on just two or three years of data and left uncertainty about the overall effect of ABS.

A nine percent fatalty increase sounds bad. A twenty-eight percent increase is an epic fail. But we’re not finished here:

On wet, snowy, or icy roads, where ABS is most likely to activate, the increase in fatal run-off-road crashes is a statistically significant 34 percent in passenger cars (confidence bounds: 20% to 50% increase). On these roads, all three types of fatal run-off-road crashes increase significantly for cars and so do fatal rollovers of LTVs.

WTF?

We are still unable to provide a convincing explanation or empirical evidence (other than the crash statistics themselves) for the increase in run-off-road crashes.

The aforementioned Mr. Williams reckons “I still think people don’t understand ABS, and when it starts pulsing and grinding they think something’s wrong and overreact. Maybe instead of spending so much money hyping hybrids, the auto companies need to do some commercials on how the safety systems in their cars work.”

So, is this a whitewash? The report’s emphasis on ABS’ net impact rather and statistical downplaying of ABS’ negative impact certainly should give NHSTA supporters pause. In fact, shouldn’t the NHTSA call for a moratorium on the technology?

But no, the report is suffused with reassurance that the next big thing in safety—federally mandated ESC (Electronic Stability Control)— will sort out the ABS “anomaly.”

Although the preceding analyses show a significant 9-percent increase for ABS on run-off-road crashes of passenger cars, the increase is small relative to the likely benefits of ESC. NHTSA’s 2007 evaluation of ESC, based on statistical analyses through calendar year 2004, found a 36- percent reduction in fatal run-off-road crashes. Thus, the combined effect of ESC and ABS is an estimated 30-percent reduction of fatal crashes.

So that’s alright then? Tell that to the families of drivers and passengers of vehicles where ABS was the difference between life and death, and not in a good way. Either that or just wait for the lawsuit.*

So, I haven't read the full NHTSA report, but has anyone actually learned or has been taught to drive a car with ABS in an emergency situation? (considering the number of idjits who've had their floormats get stuck under their pedals ought to tell you the answer to that)

I can guess that many people died simply because the ABS allowed them to control the car and steer it right over an embankment, etc.

ABS doesn't really stop the car in a shorter distance, it stops it in a more controlled manor.

ABS is supposed to stop a car in 1/4 the distance a professional driver could manage, actually. People probably just don't know how to drive (as usual) and don't know how to use the brakes, and of course most people think something is wrong when they feel the brake pedal pulsating and let off the brakes.

GameboyRMH wrote: ABS is supposed to stop a car in 1/4 the distance a professional driver could manage, actually. People probably just don't know how to drive (as usual) and don't know how to use the brakes, and of course most people think something is wrong when they feel the brake pedal pulsating and let off the brakes.

1/4 the distance........ You would think every race car on the planet would have it then.

I bet the roads would be safer if an IQ test was a requirement for a driver's license.

You drive a car with ABS in an emergency situation just like any other. The article was confusing and I couldn't find anywhere that it offered anything like an explanation for the results. Is there any proof this isn't an anomoly or (god forbid) just a statisical coincidence?

If a certain baseball team wins 70% of their games when I don't shower in the morning does that mean my not showering causes them to win?

ABS stops a car in a shorter distance than locking up the brakes... and for your average driver on the average public road, this means ABS stops the car far shorter than non ABS panic stops, and as traction decreases, ABS dramatically shortens stopping distances.

monark192 wrote:

GameboyRMH wrote: ABS is supposed to stop a car in 1/4 the distance a professional driver could manage, actually. People probably just don't know how to drive (as usual) and don't know how to use the brakes, and of course most people think something is wrong when they feel the brake pedal pulsating and let off the brakes.

1/4 the distance........ You would think every race car on the planet would have it then.

Actually, I think it is on just about every race car where it's legal. Some classes will even require extra weight for ABS-equipped cars, and teams still chose ABS with more weight.

People don't understand the purpose of ABS: To avoid locking up the wheels so the driver retains the ability to control the vehicle (steering inputs to minimize an accident or avoid collision altogether) during a panic stop situation. Unfortunately, a large part of the driving population abdicates all control when collision is imminent. They just give up and wait for the bang, especially if the car leaves the road. So the addition of ABS to most vehicles is irrelevant in the absence of any accident avoidance maneuvers.

Granted, some accidents occur so quickly there's no opportunity to avoid them or even hit the brakes. They also end up included in the statistics which skews the data. ABS can be a good thing but it requires awareness as to what it does and how it works.

What I got out of the article was that ABS can't nullify the laws of physics and there are speeds that no matter your braking system you can't stop in time.

andrave wrote: You drive a car with ABS in an emergency situation just like any other.....

Actually not in some situations. One huge advantage of ABS is that you can steer the car during maximum braking, in some situations that can be very useful. Of course few people know that, or have any practice in doing it, making it practically almost useless.

Keith wrote: Actually, I think it is on just about every race car where it's legal. Some classes will even require extra weight for ABS-equipped cars, and teams still chose ABS with more weight.

I suspect that has more to do with not flat-spotting tires when turning or braking over bumps more than it does any advantage for brake distance.

It's kinda funny how all my Daily Drivers don't have working ABS

Giant Purple Snorklewacker wrote:

Keith wrote: Actually, I think it is on just about every race car where it's legal. Some classes will even require extra weight for ABS-equipped cars, and teams still chose ABS with more weight.

I suspect that has more to do with not flat-spotting tires when turning or braking over bumps more than it does any advantage for brake distance.

A locked tire doesn't just flat-spot, it also doesn't provide any significant braking force. Since most drivers are unable to modulate the brake pressure to each wheel individually using a single brake pedal, the fact that wheels are almost always unevenly loaded under braking means that you can only brake as hard as the wheel with the least traction will allow.

If you can brake over bumps or brake while turning and your competition cannot, you will be faster.

Grtechguy wrote: It's kinda funny how all my Daily Drivers don't have working ABS

911nope, Tundra nope... race car nyet.... huh...mine either.

The wife's Xi has it so I'm not completely living ABS free.

Yeah, that 1/4 of the distance is a fantasy. have you noticed how the 100+ feet 60-0 stopping distances have dropped to 25 feet? Yeah - me neither.

I have noticed how modern cars with sticky tires and ABS have absolutely shattered the previous stopping distances of cars, even massively braked cars, without ABS. z06 corvette, toyota celica GTS, etc.

I'm not gonna argue 1/4 of the distance. In a straight line on a dry track a professional driver might be able to equal the stopping distance of an ABS car, but in the real world, we drive over greasy lines, oil slicks, wet roads, over bumps, around corners, over gravel, etc. and ABS just flat out works. Its saved me from hitting a few deer so far this year.

The article specified run off road crashes. Could it be that a locked tire has better stopping power once the car leaves the pavement. In my experience a locked tire in dirt or grass has the tendency to dig in rather than just slide. Just a thought.

Gravel or dirt roads do build up the mound in front of the tires and therefore stop better without ABS.

What I read in the article was these were extremely high speeds for the conditions and that even ABS couldn't save the drivers.

Keith wrote:

Giant Purple Snorklewacker wrote:

Keith wrote: Actually, I think it is on just about every race car where it's legal. Some classes will even require extra weight for ABS-equipped cars, and teams still chose ABS with more weight.

I suspect that has more to do with not flat-spotting tires when turning or braking over bumps more than it does any advantage for brake distance.

A locked tire doesn't just flat-spot, it also doesn't provide any significant braking force. Since most drivers are unable to modulate the brake pressure to each wheel individually using a single brake pedal, the fact that wheels are almost always unevenly loaded under braking means that you can only brake as hard as the wheel with the least traction will allow. If you can brake over bumps or brake while turning and your competition cannot, you will be faster.

Well, I guess I mostly agree on the theory except that the other tires ARE braking and the wheel that locks - using ABS isn't providing significant braking - its just not locking. There wasn't any grip there or it would not have locked. My non-abs race car isn't really hampered by its lack of ABS on lap times or ability to modulate over bumps but every now and again I get overzealous when under pressure and I release a haze of blue smoke... and that is a one huge disadvantage of not having it. My brain fades, the ABS never does.

R&T did some datamining on their road test data as part of their 50th anniversary issue. They found that acceleration rates were tapering off (this was before the most recent power surge, of course) but that braking distances kept decreasing. It was an interesting article. ABS was new enough that it probably wasn't a big contributor.

I agree that braking tests performed under ideal conditions with multiple "takes" won't show a drastic difference between ABS and non-ABS cars unless there's a real problem with the non-ABS braking system - but that the real world is very different.

Giant Purple Snorklewacker wrote: Well, I guess I mostly agree on the theory except that the other tires ARE braking and the wheel that locks - using ABS isn't providing significant braking - its just not locking. There wasn't any grip there or it would not have locked.

It can still have grip. It just doesn't have as much grip as the others. But every little bit helps, of course. Even if the one low traction tire can only provide 50% of the braking force of the other tires, that's still braking force you don't have if you lock it.

GameboyRMH wrote: ABS is supposed to stop a car in 1/4 the distance a professional driver could manage, actually. People probably just don't know how to drive (as usual) and don't know how to use the brakes, and of course most people think something is wrong when they feel the brake pedal pulsating and let off the brakes.

So your contention is that pulling the ABS fuse on, say, a 911 or Corvette will increase 60-0 stopping distance from ~100 to 400 feet? Not a chance!

aircooled wrote:

andrave wrote: You drive a car with ABS in an emergency situation just like any other.....

Actually not in some situations. One huge advantage of ABS is that you can steer the car during maximum braking, in some situations that can be very useful. Of course few people know that, or have any practice in doing it, making it practically almost useless.

Sort of. There is the whole 'traction circle' thing. By steering, you are, by definition, no longer conducting "maximum braking". I mean that, yes, there is a tremendous advantage in an ABS equipped car, especially on imperfect road surfaces, in that you can steer while attempting to stop and not have to modulate. I will say, however, that you will take longer to stop in an ABS equipped car if you do steer whilst braking.

Minor technicality, though, I suppose, I don't know how much stopping distances would be affected.

At Skip Barber we did a test with ABS and without ABS with the Dodge Neons. The differences on a dry day were virtually nil for those who could modulate a brake pedal. However, on a wet road, in unpredictable circumstances, etc. ABS can work pretty well. For the average driver, I think ABS is a huge benefit if they know how to use it (just stomp on the pedal and hold your foot there).

One person had a really good point. In most circumstances I can probably do as well with ABS as without. However, I can suffer a brain fart from time to time, whereas ABS doesn't.

I have only ever driven one car much that had ABS, and (in a safe place), made a few hard stops to trigger the ABS so i would know what to expect if I ever needed it.

I don't care much for ABS. Seems to kick in too early on most cars, like stability management. I remember driving my Dad's pickup with 4 -wheel ABS. In a rough road you wondered if it would ever stop. Pedal would go to the floor (slowly). This never happened in "normal" smooth road braking.