Emergency Brake Assist and Towing on Gravel

Submitted: Wednesday, May 09, 2018 at 10:09
ThreadID: 136669 Views:3309 Replies:11 FollowUps:15
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We had a bit of a fright recently when towing on a a very corrugated road in the Northern Flinders.

At around 60kph, on a long left hand sweeping corner, very corrugated, a roo decided to cross the road. Instinct was to put the foot on the brake quickly. Not stamp on the brake just get ready to brake. The Prado EBA decided it was an emergency and took over the braking. Foot came off the brake fast as the car went straight ahead and the van tried to pass us.

All under control again after a few ugly wriggles from the van when it’s right hand wheel entered the deep gravel on the side of the road. Thank goodness we had the road to ourselves as I used all of it to get things straightened out.

On our return to Perth I asked The Toyota Dealer if the EBA can be turned off. Whilst it may be able to be turned off (don’t know) Toyota will not allow it to be turned off.

Experience shows that brakes can be your worst enemy on poor dirt roads. Human instinct is to brake in the event of a sudden potential impact. Put the two together with EBA in play, as in our case, resulted in an interesting event that would never have occurred without the EBA intervention.

Cheers John

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Reply By: Gbc.. - Wednesday, May 09, 2018 at 10:52

Wednesday, May 09, 2018 at 10:52
Do the prado's have trailer sway control? Yes, Gravel, sand and corrugations can play silly buggers with electronics which are ordinarily great things. We had a 105 series and standard operating procedure after a number of close calls on the sand was to pull the ABS fuse - it wasn't at all well calibrated.
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Follow Up By: Member - J&A&KK - Wednesday, May 09, 2018 at 11:10

Wednesday, May 09, 2018 at 11:10
Our Prado does not have trailer sway control.
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Reply By: Duncan2H - Wednesday, May 09, 2018 at 11:40

Wednesday, May 09, 2018 at 11:40
Is "EBA" some kind of collision avoidance system? It detected the kangaroo and braked?
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Follow Up By: garrycol - Wednesday, May 09, 2018 at 14:33

Wednesday, May 09, 2018 at 14:33
Yes what is "Prado EBA"?
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Follow Up By: HKB Electronics - Wednesday, May 09, 2018 at 14:51

Wednesday, May 09, 2018 at 14:51
Emergency Brake Assist, as above apparently some in an emergency braking situation ie stamping on the brakes tend to lift their foot off the brake pedal, EBA sense the pressure coming off and reapplies maximum braking.

It can be a pain when you stab the brake pedal then realise you don't need to be braking that hard as when you lift your foot off a bit the EBA slams the brakes back on. It will disengage though when you lift you foot off but does lead to embarrassing squeal and smoke at times.

In the Prado 120 from memory it is disabled when the centre diff is locked but I don't think that is the case with the 150. The Prado Point website would be a good spot to find out.

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Follow Up By: Duncan2H - Wednesday, May 09, 2018 at 14:54

Wednesday, May 09, 2018 at 14:54
Thats bizarre functionality.. what were they thinking?
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Follow Up By: HKB Electronics - Wednesday, May 09, 2018 at 15:00

Wednesday, May 09, 2018 at 15:00
I think it is standard in a lot of models now like ABS, I suppose in reality some may not be able to press the brake pedal hard enough for maximum brake affect, others might "freeze" in a crash situation.

Once your used to it it seldom causes an issue, like the auto braking on some models that slams the brakes on if it thinks there is going to be a collision. Great feature when all cars have you'll be able to just step out in city traffic without looking knowing the cars are going to stop:) Apparently this is causing a bit of a headache for driverless cars, seems once pedestrians find out about it they are taking advantage of it knowing the car has to stop.

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Reply By: RMD - Wednesday, May 09, 2018 at 12:12

Wednesday, May 09, 2018 at 12:12
Not sure if the same system as is used or called the same, but with earlier Corolla vehicles and most new vehicles they have a Brake Assist feature built into the actual vacuum booster valving. As you brake it initially appplies more boost than you need and give a more quick application of the vacuum boosted system.
Even so, the brakes lights would have been activated and the electric brakes on the caravan should have begun operation and kept it stable.
Maybe the controller is not solidy attached to the vehicle and flaps around when under the effects of corrugation and not able to sense the vehicle decelleration correctly OR the trailer brakes are set with insufficient initial braking. If the caravan braked all should keep in line to a reasonable extent.
The above is different to ABS operation, which as mentioned above may not work well in offroad conditions. Even then the trailer should begin to brake, is your manual override of the controller handy to reach? It is those instances when it comes in very uselful.
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Reply By: bobsabobsa - Wednesday, May 09, 2018 at 14:50

Wednesday, May 09, 2018 at 14:50
Yes scares the sh=it out of you it is Not ABS or stability control it is a whole different thing
Quote from Wikipedia
Many drivers are not prepared for the relatively high efforts required for maximum braking, nor are they prepared for the "buzzing" feedback through the brake pedal during ABS operation. If an emergency develops, a slow reaction and less than maximum braking input could result in insufficient time or distance to stop before an accident occurs.

EBA is designed to detect such "panic stops" and apply maximum braking effort within milliseconds. It interprets braking behaviour by assessing the rate that the brake pedal is activated.

If the system identifies an emergency, it automatically initiates full braking more quickly than any driver can move his or her foot. Emergency stopping distances can be shortened, reducing the likelihood of accidents – especially the common "nose-to-tail" incident.

An electronic system designed to recognise emergency braking operation and automatically enhance braking effort improves vehicle and occupant safety, and can reduce stopping distances by up to 70 ft (21 m) at 125 mph (201 km/h)[2]

Brake Assist detects circumstances in which emergency braking is required by measuring the speed with which the brake pedal is depressed. Some systems additionally take into account the rapidity of which the accelerator pedal is released, pre-tensioning the brakes when a "panic release" of the accelerator pedal is noted. When panic braking is detected, the Brake Assist system automatically develops maximum brake boost in order to mitigate a driver's tendency to brake without enough force. In doing so, Brake Assist has been shown to reduce stopping distance by a significant margin (up to 20% in some studies)" end quote....

I had it on my Prado 2013 one mongrel thing .. if you hit the brakes a bit quick it thinks you are in a actual emergency and applies brute force , you nearly get seat belt burn
The 200 series is the same
I sold my prado and when back to the 100 series

I feel your pain John
cheers Bob
ps when it goes into this mode the brake lights flash to warn other drivers
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Follow Up By: Member - J&A&KK - Wednesday, May 09, 2018 at 16:04

Wednesday, May 09, 2018 at 16:04

Thanks for all the info.

As I understand it, the brake assist software measures the time difference between you taking your foot off the accelerator and putting it on the brake. If this time difference is less than a certain threshold the BA leaps into action. It definitely stayed on for a while after my foot was off the brake.

The ABS did activate but it appears that the deep corrugations caught it out as we definitely went straight on for a short time.

I have driven hundreds of thousands of kms on dirt roads usually towing a heavily laden dual axle trailer. I am well aware of the dangers of inappropriate braking and try to stay off the brakes as a matter of course. In the instance previously described the rig behaviour wasn’t such a drama and was controlled. However it was definitely a what the f*** moment.

Lesson learnt is now to “dwell a little” between lifting off the gas and applying the brake. Though it will be so hard to overcome the instincts.

Cheers John
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Reply By: David I1 - Wednesday, May 09, 2018 at 16:00

Wednesday, May 09, 2018 at 16:00
New caravans have an anti sway in them (Al -KO ESC for example) and my vehicle (LR D4) has anti trailer sway. I have felt both come into play in some circumstances. I can switch off (and sometimes do) the caravan because on dirt roads or 4WD tracks, getting on funny angles causes the brakes to be applied.
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Reply By: bobsabobsa - Wednesday, May 09, 2018 at 16:17

Wednesday, May 09, 2018 at 16:17
Yes John, it is dwell time from accelerator to brake pedal , trying to slow that down in an odear moment is hard to do , most annoying brake aid , it would definitely be great in an emergency but a quick stab of the brake and it comes into action, is not
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Reply By: 9900Eagle - Wednesday, May 09, 2018 at 19:35

Wednesday, May 09, 2018 at 19:35
All these things work really, really well on blacktop but once we enter the real world of corrugations and dirt the wheel turns. I wish I could turn abs off on dirt as it has caused me heartburn many times with both trucks, trailers and my road vehicle.

Your best friend is the trailer brake lever on your controller to keep you in reasonably straight line.
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Follow Up By: Member - J&A&KK - Wednesday, May 09, 2018 at 20:05

Wednesday, May 09, 2018 at 20:05

You (and RMD) are probably correct when recommending the use of the van brakes to keep things straight. I have never been in a situation, including this one, where such action was required. I imagine it takes a bit of practise to do such a thing.

The two tonne dual axle I towed around western NSW, with an old Landruiser, only had over ride brakes hence the effort to learn to drive on the dirt using the least braking as possible. The first trailer had drum brakes and in heavy wet black soil conditions became filled with mud. When well cooked the mud set like concrete and the brakes either failed to work or just dragged. An absolute PITA to remove the drums and free things up. 2nd version of the trailer was custom made with disc brakes, still over ride, and the problems with the mud bricks disappeared.

Many thanks for the advice on using the van brakes. However I am not sure, at my age of 70 plus that I would be able to factor that into 50 plus years of driving habits.

Cheers John
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Reply By: Kenell - Thursday, May 10, 2018 at 09:23

Thursday, May 10, 2018 at 09:23

Your story serves to remind all of us with more than a few years of "off the black top" towing experience of the odd oh sh*t moments we have. Whether it is a momentary lack of concentration, a mechanical failure or as in your case a roo wanting to race you to the ever after. We can all stuff things up on our own without a computer operated braking device buying into the argument. You have given me food for thought as I ponder my next new car which will inevitably have EBA on it. We have all heard of the ABS issues on corrugated roads but that can be disabled in most vehicles if you remember.
By the way I reckon you deserve a medal (in addition to a new pair of jocks) for being able to recover the situation. That was almost certainly due to your experience and instincts kicking in under stress. Thanks for the heads up.
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Follow Up By: Zippo - Thursday, May 10, 2018 at 14:50

Thursday, May 10, 2018 at 14:50
"We have all heard of the ABS issues on corrugated roads"

Amen to that. As a passenger in a Disco going around a sweeping gravel bend, only to see the track was blocked at a fence-line, both of us in the front seat were passengers with the feeling of inevitability as the Disco decided the where what and how. Straight ahead with pulses of brakes until we hit a tree stump and bent the substantial bar.

Had the driver been empowered to control the brake, there would have been no impact. On BB gravel the stopping distance IS shorter with wheels locked and ploughing a furrow, rather than tippy-toeing over the surface.

That Disco subsequently had an ABS-defeat switch fitted to the dash.
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Reply By: Member - Howard (ACT) - Thursday, May 10, 2018 at 22:17

Thursday, May 10, 2018 at 22:17
would be interested to know if EBA works or not if you are a left foot braker.
not into towing but often use a dab of left foot to momentarily slow and straighten things out.
in this situation there is no dwell time as foot is on both brake and accelerator so am not sure if system would work or not .
cannot test it myself as fortunately my vehicle doesnt have such nicities/nasties.
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Follow Up By: Member - J&A&KK - Friday, May 11, 2018 at 08:38

Friday, May 11, 2018 at 08:38

That is an interesting idea. I will test it today, when not towing, and advise of the result.

Cheers John
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Follow Up By: Frank P (NSW) - Saturday, May 12, 2018 at 14:08

Saturday, May 12, 2018 at 14:08
Also, what if youre in cruise control with foot off the go pedal?

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Reply By: garrycol - Friday, May 11, 2018 at 17:35

Friday, May 11, 2018 at 17:35
Another good reason to not buy a Toyota if you cannot control your own braking and the car takes over - if there is an accident, who is at fault - the driver or Toyota.

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Follow Up By: Member - J&A&KK - Friday, May 11, 2018 at 18:42

Friday, May 11, 2018 at 18:42
EBA has been fitted to many make of vehicles since about 2012. It’s definitely not exclusive to Toyota.
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Follow Up By: garrycol - Friday, May 11, 2018 at 19:23

Friday, May 11, 2018 at 19:23
My Range Rover Sport does not have it - the brakes simply work according to the brake pedal pressure applied.
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Follow Up By: Kenell - Saturday, May 12, 2018 at 12:25

Saturday, May 12, 2018 at 12:25

Your Range Rover Sport must be an older model then because according to the Land Rover website the current model has it fitted as standard. The trouble is one doesn't realise the issue until the circumstances as detailed in the op's thread arise it would seem ie corrugated road, towing a van and an unpredictable animal appears.

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Follow Up By: garrycol - Saturday, May 12, 2018 at 13:16

Saturday, May 12, 2018 at 13:16
But only if the brakes are being applied - yes the brake force being applied to the brakes increases exponentially as foot pressure increases - if you remove your foot the brakes are released - if I understand the Toyota system from the experience above the brakes stay on even if the foot is off the brakes if the system thinks the brakes should be applied.
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Reply By: Member - J&A&KK - Friday, May 11, 2018 at 18:36

Friday, May 11, 2018 at 18:36
Appreciate the comments from everyone.

Howard(ACT) suggested to try left foot braking to check if the EBA would activate.

So I tried that today on a number of occasions starting at 40 kph all the way to 100. At no time did the EBA activate. So a good suggestion Howard.

Now I have to train the brain to use the left foot for braking, even under “ instinctive emergency conditions”. Not sure how that will go. Most likely cause an accident whilst practising.

Cheers John
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Follow Up By: Kenell - Saturday, May 12, 2018 at 12:14

Saturday, May 12, 2018 at 12:14
Just put your shoes on the opposite feet, try the exercise again, and report back please.

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