Safe Speed Forums

Ive posted regarding supposed " road safety markings" in the past on the PH site, but ive not seen any mentions here of a particular problem that afflicts cars fitted with ABS systems ( a safety improvment) when encountering these dratted markings.

The scenario is one probably repeated a thousand times all over the country by ill informed, wasteful and to be frank, stupid council highways departments of whatever political persuasion.

My own experience of their "improvements" began some time ago when i aquired a particularly capable motor vehicle fitted with, you guessed it, ABS brakes.

The problem becomes apparent when attempting to stop when confronted with an emergency type situation, but its not exclusively confined to those situations.
It usually manifests itself when applying the brakes AND travelling over these "speed bars" that our council just loves to waste our money on, you know, the 2 to 3 inch wide raised bars of red tarmac designed to make us all "safer"?

What the geniuses who splattered this stuff all over the roads didnt take into consideration, was the following:----ABS works by comparing the speeds of rotation of each wheel and making a judgement call as to whether that wheel (or all) should be relieved of their braking pressure to prevent a skid situation. And therein lies the problem; The wheels hit these speed bars and either leave the ground completely (if only for a millisecond or two) or end up with a reduced contact with the road.
Now, although this isnt necessarily too much of a problem when travelling, it can become a very real danger when under braking.
The reason is thus: The wheel/s leave the surface of the road, bounced up by the speed bars, the ABS computer interprets the locking of a wheel thats not even in contact with the ground as a skid condition in the making and releases brake pressure;- Just when you need it most.

Not convinced? I had it happen 3 times to me on various roads and every time either "safety"speed bars or badly laid red "safety" tarmac was underfoot.
Now i realise that our supposed "road safety partnerships":rolleyes: will most likely come out with the old "shouldnt be speeding" remarks. Well, its odd ya know, cos in all the instances i had of this problem cropping up, not once was i "speeding"....i was STOPPING....well trying to.

Initially i thought that there was a fault with the vehicles ABS system, but subsequent investigations proved negative.

Its somewhat disconcerting to put your foot on the brakes only to have the computer remove ALL your effort on a dry road at a junction (cos this is where they apply these "safety" markings and red tarmac. On experiencing the approach to hitting a car in front, as you keep the right foot planted to the boards (reccomended advice by the manufacturers) with the ABS denying you any brakes, i decided to release them and re-apply. Brakes were then restored and i avoided a collision that wasnt my fault at all.

I have since deactivated the ABS system and have not had a repeat of the situations just described.

I have also since heard of other vehicles similarly affected, A Ford Mondeo for instance; different ABS system to mine, different software, different hardware ,affected in exactly the same manner.

I contacted my local Highways department about their usage of this red tarmac and speed bars and was basically told that there was a fault with the car by an idiot who most likely dosent even drive and has no comprehension of what an ABS system does, let alone how its affected by moronic decisions made by, er, morons...
I left them with a promise: The first person who dies as a result of this stuff and ill make sure the newspapers hear all about it and they cant say theyve not been warned.

Whilst im on a roll here, has anyone else noticed the upsurge in bad lane discipline caused exclusively by highways departments incompetence in markings on traffic islands?
There are NONE. No lane dividers...nada, zilch!
The results are concerning.
On a 2 lane approach to an island, people in the left lane going round the OUTSIDE to reach their exit....on the 3rd or 4th????
Why havent they marked a clear lane division?
Left lane:Left or STRAIGHT ON.
Right lane: STRAIGHT ON or RIGHT?
Instead, we take our lives in our hands as these confused drivers wander from place to place forcing others to make allowances.

Wheres it all going? Who the hell knows, Downhill is my guess.
Only 2 expaanations can be possible: Deliberate mismanagement or incompetent stupidity. In either case, a wall, a blindfold and a last request (optional) are the cure.

Ok, who's first?

One set of markings I heally hate is those lane markings on roundabouts that force you into unnatural positions on the road instead of the natural line. You tend to get lane changing in stupid places as people realise that the lane they are in is suddenly not going where they want.

I agree that the "left hand lane and turn right" brigade are a menace.

_________________
Malcolm W.
The views expressed in this post are personal opinions and do not represent the views of Safespeed.

I have often wondered about the effects of those rumble strips they put on the approach to 30mph zones. Especially where bikes are concerned.

I have seen them on the approach to a bend, where one would normally be braking and though I have never had any problem in a car (ABS equipped or otherwise) I often thought they could prove disaterous for bikes.

Co Durham seem fond of these, any comment IG? Lots of them in the Middleton-in-teesdale, Romaldkirk, Barnard Castle area. One set are flattened i.e. don't have the rumble effect but still, braking and paint are not the best mix.

whos ABS systems are we talking about?
what year of manufacture?

(those rumble strips are nasty on a bike (proper one with pedals ))

Well in my case, Toyota, 1991. The Mondeo i mentioned...i cant tell you.

I really dont think the type or year involved will actually make much of a difference, unless theyre vastly different in either programming or hardware, but i cant see there being a huge difference between the marques, and in any case, they all work in the same fashion, as far as im aware.....(stands by to be corrected..)

There are massive differences in ABS capability - and the capability will depend a lot on age.

The original units were single channel, and intermittently released the pressure just after the master cylinder, thus dropping pressure to all wheels simultaneously. You can get into a real mess with these in low grip situations, such as creeping down an icy road - one wheel locks and braking to all wheels is lost giving you an un-braked decent. If you have a single channel ABS seriously consider pulling out the ABS fuse when there is a lot of ice around.

The later units are typically 4 channel, with independent control to each wheel - these are much less likely to let go, and will typically maintain maximum available grip to all wheels.

Intermediate models were two channel (normally working on diagonally opposite wheels).

I also don't like rumble strips, which are really mini speed bumps, and I hate speed bumps with a vengeance. They are incredibly dangerous things that cause delays in emergency response (Fire, Ambulance), cause serious discomfort and pain to those with back injuries (as I had for a while) and a seriously distracting. To make things worse, the don't even work unless they are built like monsters or are very sharp. Small ones (3 or 4" high, 18" across) are much more comfortable at 50mph than they are at the 30mph limit that they are supposed to enforce. The more vicious ones are worse for all traffic full stop.

The reason why I don't like them, and most of the road safety markings is that they are a complete insult to intelligence, and often have exactly the opposite effect to that intended. I have already covered speed bumps that get more comfortable at higher speed, but high grip surfaces (red) in front of traffic lights provide maximum grip for a light controlled start to a drag race; elsewhere they just make it harder to work out what you are supposed to be driving on.

I'd never noticed that particular side effect.

_________________
Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

I'd wonder about my driving if I managed to even get anywhere near my abs kicking in. Perhaps paying more attention to what's going on ahead would help - unless you're just like an old friend of mine who liked to perform an emergency stop at every intersection.

well they'd like you to think they all work the same
and its such a 'mature' system there is alot of convergence in performance.

i meant the manufacturer of the abs not the car... you'd only know from the label on the valve block or ECU.

oh dear.. double posting....

i had the opposite problem a while back, the car ahead looked to be going across on amber but decided to stop. think i was distracted for a short moment and had to stand on the brakes as my braking distance had now got shorter by a car length.
both cars now deccelerating a much as grip would allow. sadly the car infront was on the red delugrip surface whilst i was still on tarmac.

(yes yes a bit ore anticipation and caution on my part would have avoided the issue.. but there it is)

and a third...

the issue here is that you dont have to be anywhere near normal ABS activation for it to kick in for a few cycles.

just try moderate braking over a bump, or over a manhole cover.
one wheel suddenly has less grip ( reduced surface friction, reduced vertical load(aka airborn) ) starts to lock.
ABS behaves as it should/must and takes pressure off that wheel to prevent it.

of course it has no way of knowing that half a second later that wheel is going to be back on nice grippy tarmac.. and it takes a few cycles to work out that it is.
which is why the whole thing feels underbraked for a brief period.

and this means that it happens at a level of braking thats nowhere near what is required for a full ABS stop on dry tarmac.

(i've tested and developed a number of ABS systems and never come across a system that either removes ALL pressure from a brake or requires you to fully release the brake and reapply in order to restore pressure to a brake)

well my traction control often kicks in in those situations, even though it's not needed, but I've been driving abs equipped cars for around 6 years now (and I know I've been on the brakes on those warning bumps) and the abs has only come on once (not counting track days) and that was entirely my fault as I allowed myself to be distracted.

Oh i see.....my drivings at fault.....stupid me for not noticing!

Spot the clean driving licence with a lack of accidents and my driving seems to be fine.

funny, that's what most drivers say. Nothing wrong with my driving, nothing I can improve. I do the speed limit and have never had an accident - pity about the trail of carnage behind me.

So tell us then, why have you, on serveral occasions - and those are just the ones that you're telling us about - been on the brakes hard enough for your abs to kick in? If that's not telling you something then why not take a poll and see how many people on here have managed to activate their abs in the past year, and why.

I have, on loose gravel - no particular braking force involved, I was pulling over to look at the road atlas.

I have too, because I regularly test the limits of braking when I am alone, just so that I understand how the car will react.

However in normal driving, then last time was when it snowed, and with the usual lack of local gritting I had a little ABS activity until I had a better feel for the available grip. Not activated because I needed to brake harder, I was just slightly to heavy on the pedal for the conditions.

You obviously havent read what i originally posted. Either that, or you wish to start an argument....nil desperandum, i can accomodate both scenarios equally.

The ABS kicks in when braking on SPEED BARS and badly laid RED TARMAC, ie when its laid by hand with ridges.

The braking force i used when i encountered this problem was no more fierce than at any other normal braking time, but, for the reasons explained in my first post, i lost braking action.

I feel sure that if i had kept my foot planted on the pedal id have had an impact, albeit a slow speed one.
Since disabling the abs system i havent encountered the problem again.

As regards your insinuations of a trail of carnage: How can i put this without being indelicate?......Bollox!

I drive using the safespeed rule, which my friend is why i am accident free(bar one minor screw up some 4 years ago).
I also do not stick to the speed limits. I break them! And yet i have no endorsements or speed related crunches.
Explanation? I must be doing something right.

Yes, my driving most likely could be improved in some way, but ill bet yours also could.

Read the post and understand it before going off on a tangent please.

I had this happen to me a few days ago, which left me puzzled - I know from previous deliberate ABS activations to get a feel for the system that in this instance the level of braking wasn't anywhere near where I'd be expecting the ABS to kick in. Now it makes sense, since most of the main road junctions around here have been treated with either red or beige coatings, and I was approaching one of these at the time.

Brilliant! Thanks for that Twister.

What vehicle do you drive btw? Mines actually 4wheel drive so it shouldnt have ocurred to me as dramatically as it did as all wheels are connected full time.
What speed were you doing when you had this problem? From what i remember, i was doing approx 20 ish on the slowdown and as soon as i hit the red stuff i lost the brakes.

Id be interested to know how many other instances of this are happening.

Vauxhall Omega (RWD, 4-channel ABS), doing about 35. As my pressure on the brake pedal increased (I tend to brake progressively on, then progressively off, unless there's a clear need to stop ASAP...), I got maybe 2 seconds of pedal judder consistent with an ABS activation, which then ceased as my speed continued to drop.

Other than the pedal judder I wasn't aware of any problems in braking - as Rewolf points out, with a good multi-channel system you don't lose as much braking effort if some wheels are still able to brake without intervention, so given the momentary nature of the activation I wasn't concerned about it being a safety issue. Indeed, until I read your post, the thought that some ABS-equipped vehicles might react poorly to such a road surface hadn't even occurred to me.


Also, I've noticed that some of the high-grip coatings (moreso the beige coloured stuff than the red stuff) around here seem to be wearing off rather rapidly, leaving patches of fairly smooth looking tarmac underneath. I wonder if "false" ABS activations could also be caused by varying grip levels as one or more wheels pass over these worn patches?