ABS on Cars: Good or Bad Thing?

One car I had only had abs on the front,
There are a variety of circumstances where that might be better in some ways

 

NO.

I has been proven over and over and OVER that a properly working ABS system coupled with your "average" driver will reduce your stopping distance in a panic situation. And with just a tiny bit of training so that you actually STEER during the skid, your situation improves even more.

Only professional drivers who make a living racing or doing other things that causes wheels to lock and the vehicle to skid are ever able to achieve better results without ABS.

The testing did occasionally find a "normal" driver who was better off without ABS but that was something on the order of one in a million.

 

Not according to Toyota - this from the Prime owner manual: "The ABS is not designed to shorten the vehicle’s stopping distance."

Edit - the Pre-Collision brake assist can reduce stopping distance in a panic situation:

Pre-collision brake assist

When the system determines that the possibility of a frontal collision is high, the system applies greater braking force in relation to how strongly the brake pedal is depressed.​

 

In most cases, when those systems don't work as the driver expects, or become hindrance, aren't during critical times. If traction control is going to work against me on a snowy incline, I had feedback previously during the drive that let me know wheel spin may be needed for crawling through the snow.

With ABS, you might be able to experiment to see if stopping distance will be shorter without it, but you aren't going to know if you need stopping distance or for a panic stop until you are in the middle of it, and very likely don't have time to turn it off or on if you guessed wrong.

The conditions in which ABS is compromised, non-ABS is also compromised. In addition, control is also compromised. I can't say how many, but I know some accidents that occur under those compromising conditions were the result of a lack of control, and lack too long braking distance.

If there is snow or ice on roads, you be going slower and giving more room no matter how the car is equipped.

My Ranger had rear ABS standard. I thought of it as feedback as to when I was reaching the front brakes limits. Ford was probably thinking providing more control for the too light back end. You learned to expect unexpected rear end kick outs with that truck.

 

In deep snow or gravel, you can stop more quickly with a locked wheel than with ABS active. So, even though stopping distances on loose surfaces are worse than on hard dry surfaces, ABS makes the problem worse compared to no ABS. That's why it would be helpful to have an override. For the same reason that people who take Outbacks offroad pull the ABS fuse.

 

You sure about that? Much of the problem ABS was created to solve is the phenomenon of the rear wheels locking up and taking your directional control.

 

And why non-ABS is preferred for off road trucks.
But street cars aren't going to be doing technical descents on steep grades. The gravel roads they might see are low speed, and likely compacted to the point of no longer being loose. Gravel packed into dirt does behave differently than scree and fresh dumped.

In the case of snow, if you are going fast enough, or are close enough to the car in front, that the difference between having ABS or not actually makes a difference, you are going too fast or are too close.

 

That's all true, but I'm still curious why the option is not offered to disable ABS temporarily for those situations where it can extend your stopping distance. Even if it could be disabled for the rest of the drive and then reset on the next car start.

You can make the same argument for dry pavement - if you ever activate ABS are you too fast or too close?

 

Either way...A/S, ABS or whatever you want to call it's variances...are required by law now.

 

For non-ABS to provide shorter stopping distance on snow or gravel, the wheels have to lock up. That means giving up the ability to steer. If that shorter stopping distance isn't going to be enough, steering around the object is no longer an option.

Since the driver can't know if they need stopping distance or control during an emergency, leaving ABS on is probably the best option as it helps more often.

GEN3 and earlier Prii, and possibly other Toyota hybrids, did not let you turn off traction control nor VSC. So option to turn off other safety aids isn't always available.

If you had to threshold brake, were you driving too fast or too close?

With snow on the roads, you have to slow down and drive more carefully. If you have ABS take that into account, or disable it, or perhaps just learn how to brake on snow when equipped with it., "In snow, the driver needs to stop slowly by softly depressing the brakes to prevent engaging the ABS. This will actually create a shorter stopping distance than hard-braking and activation of the ABS. A softer surface requires soften stopping." - Driving With ABS in Snow and Ice | YourMechanic Advice

From the same site and year as the OP on disabling ABS for snow, Disabling ABS to Drive in The Snow Is An ‘Extremely Bad Idea’
“I would say it’s an extremely bad idea,” said Mike Rizzo, Technical-Fellow for Chassis Controls at General Motors. “If I’m driving and let the front axle lock before the rear axle, I’m going to get into a situation where I have terminal understeer … and the vehicle is not going to want to turn.”

Short answer: Steering > No Steering. Disabling anti-lock brakes also disables traction control, which the National Highway Traffic Safety Administration estimated reduces fatal vehicle crashes by 30 percent in sedans and 63 percent in SUVs.

Rizzo said he frequently hears the questions, and the logic behind disabling ABS isn’t entirely unfounded: Piling snow in front of dead-straight wheels would shorten braking distance. Digging in is better. Threshold braking makes for safer stops.

“In all reality, the computer is better and designed to (pump the brakes) faster than you can,” he said.

Rizzo said he’s often asked why engineers can’t program an ABS controller that could recognize when the wheels are straight and allow drivers to lock up wheels to “wedge” snow in front of the wheels.

“That’s technically correct in a test environment on a highly deformable test surface — meaning you can get a ‘wedge’ in front of a tire — but I would say that’s more applicable to gravel than snow. Snowy surfaces are generally more polished, even with just a little bit of traffic on them,” he said.

Even with studded tires, rotating wheels are directly proportional to steering control. Locking wheels effectively makes the car uncontrollable.

“When you get on very slippery surfaces and lock the wheels, it can take seconds for those wheels to start spinning back up to the velocity of the vehicle. There’s not a lot of road friction to push back on the tire to start spinning them back up,” he added."

 

I understand that. Is there any regulation that prevents a manufacturer from providing a temporary disable function?

Electronic stability control is also required by law on automobiles, but NHTSA allows temporary disabling of that system.

 

ESC needs to be disabled for running a car on a dynanometer, like for EPA testing. Then there times, like starting in snow, where careful driving alone isn't enough which, makes turning off ESC is the only solution. I once couldn't go into work because the gen2 Prius doesn't have a switch to turn off ESC.

As whether it is legal for manufacturers to provide a way to disable ABS, you have to ask NHTSA. Depending on the system, it may not be possible to disable ABS without also disabling ESC and VSC.

 

Yes, there is: FMVSS No. 135, S5.3.2, mentioned in my November 2018 posting, which has other references that may interest readers of this thread. The reason for it is briefly explained in the final rule, Federal Motor Vehicle Safety Standards; Hydraulic Brake Systems; Passenger Car Brake Systems, 60 Fed. Reg. 6,411 (Feb. 2, 1995), at 6,414 (PDF; see page 4, under “ABS Disabling Control Switch” in the second column).

 

Wow, nice find!

TL;DR version: Toyota asked for permission for a disable switch, Ford & Chrysler asked for a provision for an intelligent automatic switching system. Mercedes, Ford & Chrysler specifically said it should not be driver-controlled.

 

Many thanks. Just what I was looking for.

 

So.....what do you think it IS designed to do ??
That statement, by itself, is grossly misleading.

It is designed to prevent total wheel lock up when braking hard.
Under most conditions, that WILL shorten the overall stopping distance and keep the vehicle pointed in the right direction when panic braking.

Versus having all 4 wheels sliding and having no steering control at all, it absolutely WILL reduce the overall stopping distance.

Again, under the worst conditions, including wet and icy roads the system is most useful.

Of course it will not "shorten the stopping distance" under normal conditions; you do that by pushing the pedal harder.

 

I remember, guessing 15 years ago, in a 94 Intrepid (old mopar ABS) on the Hwy at 4am doing 70.
(3 deers) were standing in the middle of the Hwy. After the fact I called them kamikaze deer s .... By the time I eyed these creatures wandering the Hwy, I knew I was up sheets creek. As quickly as my widdle booted foot would move, I slammed that brake pedal. I doubt the ABS even had time to calculate the rate of pulse to use.
I remember thinking, I'm not going to make this one. About 10 or 20 feet from the 3 deers I swerved hard left than hard right again and managed to fishtail around the unsuspecting creatures just standing in the middle of the road watching me. I was still traveling at a decent clip when I swerved and almost lost control. That wouldn't have ended well either. I guess the ABS did it's job in my case, but if it had been just a hair different the results wouldn't have been pretty. So there are limits to ABS effectiveness, even if they are far beyond our typical drivers capability here on most US Hwys'

 

If you believe ABS threatens your safety, disable it. If not under a single fuse, resistors can replicate the values.

Go with God! BUT hands off my ABS!!!

Bob Wilson

 

All this time I thought John Muir died about 100 years ago before there were very many cars anywhere.

Mike