Emergency Braking - what's your definition?

[ZZZZ]

When I initially configured my Adaptive Brake Light unit, I looked into what would be considered an emergency braking, or very rapid deceleration, and set the parameters accordingly - at 0.5G threshold.

Now, I have just had an enquiry from a chap, who bought one of my units, expressing dissatisfaction at the fact it didn't flash, when he went from 60mph to a complete stop in exactly 100 yards.

That translates to 0.39G, so the unit didn't react (deceleration of 12.9ft/s2).

I don't know about others, but I wouldn't want my brake lights to flash, when I simply coming to a stop, or slowing down faster, than normal, but still not what I would call 'mash the pedal to the floor' situation?

Even the Highway Code gives that magic 73m stopping distance for 60mph, and that's exactly 0.5G or 4.9m/s2.

What would you consider to be an emergency braking, when you'd expect your adaptive brake lights to kick in?

 

[LostKiwi]

I think in the wet you could be hard pressed to stop at 0.5g so I would say 0.33g would be a good value. In my thinking is that a rapid stop would also be a desirable time to warn others of something out of the ordinary happening.

 

[ZZZZ]

Thanks, that's a very good point ... I wonder if OEM system takes that into consideration, probably does - ESP, etc.

The 0.5G came from OE figures (not MB though - didn't see theirs in open sources).

 

[John Laidlaw]

^ I’m with this- or a sense check (OK I know it’s not exactly the same thing!) to me would be when ABS kicks in

 

[LostKiwi]

^ I’m with this- or a sense check (OK I know it’s not exactly the same thing!) to me would be when ABS kicks in

Good point - triggering from the ABS would also help identify when braking hard on snow/ice/mud etc.

 

[ZZZZ]

Would be easy enough to implement for Mercedes cars ... Hmmm I still got a dozen of PCBs left ...

 

[alexanderfoti]

I believe MB flashes the lights when the ABS engages, so it varies based on road surface.

 

[LostKiwi]

Would be easy enough to implement for Mercedes cars ... Hmmm I still got a dozen of PCBs left ...

You could cover both bases... When g>0.35 OR ABS=True -> Flash brake lights.

 

[Wighty]

I believe MB flashes the lights when the ABS engages, so it varies based on road surface.

Thats what i understood as well . I would say emergency braking is when you have misjudged sonething and you are trying to put the pedal through the floor .

 

[John Laidlaw]

You could cover both bases... When g>0.35 OR ABS=True -> Flash brake lights.

Excellent thinking!

 

[ZZZZ]

Only a dozen PCBs left, and I'm not making any more, but I suppose I can do a customised MB version, based on that ^^
Won't be a DYI install in this case though ...

 

[Submariner1]

I think in the wet you could be hard pressed to stop at 0.5g so I would say 0.33g would be a good value. In my thinking is that a rapid stop would also be a desirable time to warn others of something out of the ordinary happening.

When I initially configured my Adaptive Brake Light unit, I looked into what would be considered an emergency braking, or very rapid deceleration, and set the parameters accordingly - at 0.5G threshold.

Now, I have just had an enquiry from a chap, who bought one of my units, expressing dissatisfaction at the fact it didn't flash, when he went from 60mph to a complete stop in exactly 100 yards.

That translates to 0.39G, so the unit didn't react (deceleration of 12.9ft/s2).

I don't know about others, but I wouldn't want my brake lights to flash, when I simply coming to a stop, or slowing down faster, than normal, but still not what I would call 'mash the pedal to the floor' situation?

Even the Highway Code gives that magic 73m stopping distance for 60mph, and that's exactly 0.5G or 4.9m/s2.

What would you consider to be an emergency braking, when you'd expect your adaptive brake lights to kick in?

I have adaptive brakes and adaptive brake lights (flashing).
I rarely see them flash at night ( sort of rear reflection). Initially I thought they didnt work.
But they do!

Cant assess G force etc.
Emergency Braking imo is like full power brake depression, They would definitely flash then.

These adaptive brake lights flash when you are braking pretty hard, but well before ABS kicks in.
I.e. in normal driving with no drama then they won’t come on. But any more than normal driving, then they flash.
E.g. if someone is trailling me too close, if I speed up and widen the gap, and then brake sharply (but only to the point the car behind is then at the original distance) then they will flash. Note after braking sharply I always speed up again in case they are not attentive.
The flashing works ... they seem to realise this CL can stop dam quickly, and back off.

I would like them to flash a bit earlier than they do. Ideally whenever one brakes significantly harder than normal but well before an emergency situation.

In your shoes as a supplier, I cant see a downside if they start flashing at anything above normal road use braking. I wouldnt want them to flash in normal daily useage.

I guess Mercedes is a little more “flashing” conservative, because of all the other things adaptive braking does (which on this car is linked to the flashing).

Caveat: I don't use my brakes very much, my pads and discs generally last a very long time. Just by road awareness and situ anticipation the big engines bring down the speed sufficiently a lot of the time.

Hope that helps.

 

[LostKiwi]

if someone is trailling me too close, if I speed up and widen the gap, and then brake sharply (but only to the point the car behind is then at the original distance) then they will flash. Note after braking sharply I always speed up again in case they are not attentive.

Be aware that in the eyes of the law that behaviour (known as brake testing by some) is illegal and classed as dangerous driving.
Even just flashing your brake lights without actually slowing down is classified as Driving without due care and attention.
I know this from bitter experience where I was prosecuted and found guilty of flashing my brake lights and only had it overturned after a lengthy and costly appeal.

Obviously automated flashing devices for warning drivers of a situation where the car in front is slowing rapidly due to a developing legitimate situation in front of the vehicle is not subject to the same legal interpretation.

 

[Submariner1]

Be aware that in the eyes of the law that behaviour (known as brake testing by some) is illegal and classed as dangerous driving.
Even just flashing your brake lights without actually slowing down is classified as Driving without due care and attention.
I know this from bitter experience where I was prosecuted and found guilty of flashing my brake lights and only had it overturned after a lengthy and costly appeal.

Obviously automated flashing devices for warning drivers of a situation where the car in front is slowing rapidly due to a developing legitimate situation in front of the vehicle is not subject to the same legal interpretation.

Thanks very useful to know.
Totally agree with the brake jammer scenario being illegal.
Like the prats that for whatever reason overtake you and and then slam the brakes on, where only your superior brakes or distronic stops you from rear ending them.

But you are saying the following is also technically illegal:-
My rear camera is on, we are in a queue, driving then stopping. Every time I stop slowly the car behind comes up really fast and just about stops, it is recorded 3 or 4 times. He is so close, you cant see the front end of his car! He does this repeatedly.
So I speed up and get three car length ahead, and when the traffic in front stops, I stop quickly activating flashing AB. He naturally comes up behind quickly, the gap narrows to 2 two lengths, and when it looks like he is 2 car lengths away I conciously move off to make it 2.5 car lengths, and then come to a stop really slowly say 1/2 a car away from the car in front.
I.e. just demonstrating my car stops fast. No intention of putting him in danger, and in fact ensuring he is further away than he was repeatedly doing.

Note I am not braking when the road ahead is clear, only when I am actually having to stop.

As I have a recording front and rear .. how would they say that was dangerous.
I could prove:-
1. he was constantly coming up far too fast and far too close.
2. My actions never put his car closer to mine, that he did on numerous occaisions
3. If I hadn't braked (the front camera would show) I would crash into the car infront.

Can’t see how I would loose that one.

But appreciate the info , because imo its a totally crazy country. Like the “pensioner” was charged with assault, when he hit a burglar, who broke into his house and started a fight.
The pensioner had no record, the would be thief had a string of offences for burglary, assault and GBH!
Beggars belief the CPS didnt instantly throw it out.

 

[Ken_R]

You could cover both bases... When g>0.35 OR ABS=True -> Flash brake lights.

Not sure if it helps with the question but back about 1980, when we took on board from the USA, the subject/science of Accident Investigation by Mathematics, I attended the course(s). At the time it wasn't 'accredited' but was later recognized by the City & Guilds.

That said, just out of interest, I 'back calculated' the Braking distances as set out in the Highway Code and, from memory, it worked out that it was based on a Coefficient of Friction [of the road surface] of 0.7 (of Gravity), being typical for a normal dry road surface.

Back then, to measure the CofF [of the road surface], we had a vehicle that effectively fired chalk (onto the road) from a shotgun, at a known time interval - with the wheels locked. I'm sure the technology has since moved on.

Similarly, whilst they now use GPS locators for determining positions, back then, we used two 30 metre tape measures at right angles, and had to write it all down.

 

[L John]

The OP said the driver claims to have gone from 60 mph to a complete stop in 100 yards.
I guess the driver was unhappy because that is rapid deceleration and a car stopped on the road from an initial 60 mph is likely to pose a danger.
The driver should have used hazard warning lights in this case, whether brake lights were flashing or not flashing is irrelevant.

The units sold by GLK are not advertised as a fully intelligent retrofit.
If I did the same thing in my car with the factory adaptive braking/lights I doubt it would have flashed in the same situation unless the road was slippery as others have stated.

From my view GLK has done a cracking job with a unit that WILL flash the brake lights with an emergency stop on a good road.
Anyone wanting more should go to MB and see what the price of a retrofit is.
The buyer knew what he was getting, if he wanted more he bought the wrong thing.

GLK, my advice is don't try to do more with your unit, it does what it says on the tin.
Any further advanced unit you make, e.g looking at the ABS etc will cost more and need more work to fit, you wont get any buyers.

Tell the driver to do a simulated emergency stop on a dry road and let you know if they don't flash (I'm sure they will).
An emergency stop in this case would be maximum braking force, not just rapid deceleration, although the lights will flash below maximum braking force, there will be a point where the parameter is not met.

 

[ZZZZ]

Thanks! Appreciate your support

I'm not making any more of these - my enthusiasm for the gadget wasn't matched by the general public ... at least not without some marketing trickery, mostly through 'social networking', which I'm not a master of, and rather dislike ('can't stand' would be an honest description).

 

[Submariner1]

The OP said the driver claims to have gone from 60 mph to a complete stop in 100 yards.
I guess the driver was unhappy because that is rapid deceleration and a car stopped on the road from an initial 60 mph is likely to pose a danger.
The driver should have used hazard warning lights in this case, whether brake lights were flashing or not flashing is irrelevant.

The units sold by GLK are not advertised as a fully intelligent retrofit.
If I did the same thing in my car with the factory adaptive braking/lights I doubt it would have flashed in the same situation unless the road was slippery as others have stated.

From my view GLK has done a cracking job with a unit that WILL flash the brake lights with an emergency stop on a good road.
Anyone wanting more should go to MB and see what the price of a retrofit is.
The buyer knew what he was getting, if he wanted more he bought the wrong thing.

GLK, my advice is don't try to do more with your unit, it does what it says on the tin.
Any further advanced unit you make, e.g looking at the ABS etc will cost more and need more work to fit, you wont get any buyers.

Tell the driver to do a simulated emergency stop on a dry road and let you know if they don't flash (I'm sure they will).
An emergency stop in this case would be maximum braking force, not just rapid deceleration, although the lights will flash below maximum braking force, there will be a point where the parameter is not met.

I think the cost of an MB sourced Adaptive Braking retrofit would be pretty mind numbing :-/
And thats IF it could be done .

 

[C350Carl]

I can't comment for MB as luckily can't recall having to emergency brake in mine. So not sure if my S212 even has it (be surprised if not given it's a 2013 car).

However in my vRS the car did two things. If you did brake hard then brake lights would flash and if, whilst the flash had been triggered, you came to a complete stop the hazards would automatically engage. They would only then switch off manually or once you went above 20mph.

I can't tell you what the force was that needed to be applied as the only time I recall it being put to the test was when I exited a bend on a 60mph road to find another car sideways on it's roof across the road in front of me and my friend following commented in how useful the flashing brake lights and auto hazards had been to warn him.

 

[Brizzle]

According to the data sheet for my 2009MY W204 it has "adaptive stop light flashing" - I guess that's what we're talking about. To the best of my knowledge I've never triggered it - how would I know anyway? - but TBH if I was in a situation where I was braking hard enough for it to trigger the last thing I'd be doing is looking to see if it's working. It's much more likely I'd be looking for somewhere safe to steer the car to avoid whatever was in front of me.

Anyone that thinks stopping from 60mph in 100yds is "heavy" braking needs their senses re-calibrated. The overall stopping distance given in the Highway Code (which regularly gets ridiculed on here and elsewhere) from 60mph is 240ft - that's 80yds for those that are arithmetically challenged or 73.15m for the metrically minded

@GLK: Tell him it worked precisely as intended and to drive more carefully in future