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Mbokane and Another v National Employers' General Insurance Company Ltd. and Another (280/93) [1995] ZASCA 92 (12 September 1995)

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CASE NO: 280/93


In the matter between:












I have had the benefit of reading my brother

Smalberger's judgment. My disagreement with his conclusion relates to the critical question whether the appellants have proved, as a matter of probability, that the driver was negligent in continuing on his way knowing that there was something wrong with one of his tyres.

For negligence to be established on the part of the driver before the tyre burst the appellants have to prove two things. The


first is that the bus was driven for a considerable distance with an
under inflated tyre, which led to the building up of heat and the
eventual destruction of the tyre. The second is that the driver should
have been aware of the under inflation and ignored it.

I shall deal with the latter point first. All the evidence

is to the effect that everything was going normally until the bang
which signified the bursting of the tyre. There was no hesitation by

the driver, no wrestling with the steering wheel and no slowing down.

When dealing with the under inflation theory in cross-examination

Harre said:

"But surely if the tyre was partially deflated there would be such a drag on the steering that the driver would know that he has a partially deflated tyre."


That evidence is not contradicted. But even if little or no weight is attached to it the form of negligence under discussion is premised upon awareness of something wrong on the driver's part. I find it most unlikely that a bus driver faced with such a drag on his steering wheel would continue on his way blithely as if nothing had happened, putting at risk not only the lives of his passengers but also that of himself. So that, however much I agree with my brother Smalberger as to the driver's duty if he had felt that something was wrong, I cannot agree with his conclusion,

I return to the first point,has it been proved that the tyre was under inflated? There is no direct evidence of any kind on this point. The only evidence that there is is that of an expert on either


side, Mr Keuler, a rubber expert from the SABS who was called for the appellants, and Mr Harre of Firestone who was called for the respondents. He has been with Firestone since 1967 and his expertise includes the identification of the causes of tyre failures.

Keuler's theory (I doubt that it is an opinion) is that the bus was driven for a considerable distance with the tyre under inflated or the bus overloaded. The flexing caused to the side wall each time the tyre reached the bottom of a revolution would lead to the building up of a lot of heat, which might lead to the bursting of the tyre. Harre's opinion, by contrast, was that the tyre had burst as a result of an impact fracture, caused by its striking a hard sharp substance of substantial size, such as a stone.


I have said already that Keuler's theory seems to fall short of an opinion. He based himself mainly on a blueish discolouration of some of the rubber which was the result of heat. Such heat in the tyre, he said, was "normally" the result of overloading or under inflation. The fact that the side wall was ripped was also "normally" a sign of the same. But he agreed that he could not be categoric, that there are all sorts of possibilities, including impact damage caused by a stone of substantial size or a pothole. He was questioned as to whether the heat could not have been generated after the tyre burst, whilst it was being mangled before the bus hit the bridge. He seemed to doubt that the distance would have been sufficient, but he did agree that the flexion after bursting would have


been much more than during under inflation before the bursting.

Harre accepted that bursting because of under inflation
was "a thing that can happen". But he did not consider that it was

the cause in this case. He placed considerable emphasis upon heat

inversion. As I understand his evidence, when rubber is heated (in

the course of being vulcanized) it is strengthened, but if too much

heat is applied thereafter it is weakened again, reverting to its original

state. In explaining why he did not believe that the under inflation

theory was the correct one, he said:

"1 believe that the amount of heat generated from extended running in either the overloaded or under-inflated condition will cause the interface separations which will show a stickiness that comes from the rubber being excessively heated and the interfaces separating.


This case here it is actually not interface separation, it is actually torn. It is torn apart rather than separating."
Although his inspection for stickiness was confined to

visual examination and was not backed up by any test, I consider that
weight should be attached to his experienced eye when he says that
there was a tearing not a separation caused by heat. Although Keuler
was not fully cross-examined on this subject he did accept the theory

of heat reversion. After this concession the following appears:

"He will also say (Harre) that there was no evidence present on any of the pieces of tyre available for inspection of such heat induced reversion of the rubber. ... I would not be able- to argue against that. The question is how was that determined?"

At the Bureau of Standards, he said, the presence or


absence of heat reversion could be tested. But he himself performed
no such tests. Keuler also said that one would find the stickiness
only in a "very advanced state of reversion" . Harre took this up and


"Mr Keuler testified that you only get a sticky tacky texture to the tyre in a case of a extreme heat inversion. Yes but it takes that type of heat to get the separations occurring in a tyre."

Harre also said that he did not observe any substantial

amount of blueing, and that such as there was could have been

caused by the tyre being stored exposed to the sun.

All in all I am considerably more impressed by the

evidence of Harre than that of Keuler. But all that I need say is that


I do not consider Keuler's evidence to be superior to that of Harre, and for that reason I do not think that the appellants have proved on the probabilities that the bus was driven with the tyre in a state of under inflation.

It is true that no sharp object was produced. I do not find that surprising given the conditions that must have prevailed after this awful accident. Not even all of the burst tyre was retrieved, which has contributed to or even caused the appellants' difficulty in proving what caused the tyre to burst. Moreover, the driver is dead.

In the result I do not think that the appellants have proved either of the two things that it was incumbent on them to prove, or, consequently, that the driver drove negligently before the


tyre burst.
The appeal accordingly falls to be dismissed, and consequently also the condonation applications referred to in my brother Smalberger's judgment. I agree with him that the appellants' Pretoria attorneys should bear the wasted costs of applications (c) and


The following order is made:

The condonation applications are dismissed. The appellants are to pay any wasted costs occasioned by the applications relating to the late filing of their notice of appeal and their powers of attorney, jointly and severally. The appellants' Pretoria attorneys are to pay the wasted costs occasioned by the applications relating to the


late filing of a proper record, as well as an additional volume of the

The appeal is dismissed with costs to be paid by the

appellants jointly and severally.




Early in the morning on 8 November 1988 a bus fully laden


with passengers, which was en route from Kwaggafontein to Pretoria, left the road and overturned ("the accident"). The immediate cause of the accident was a burst right front tyre ("the blow out"). The driver of the bus, one Moses Koloi ("the driver"), and several passengers were killed in the accident; a number of other passengers, amongst them the two appellants, were seriously injured. The bus was owned by the second respondent ("Putco") and the driver employed by it. At the time of the accident he was driving the bus in the course of his normal duties. The first respondent ("NEG") was at all relevant times the duly appointed agent of the Motor Vehicle Accident Fund in terms of the provisions of sec 6(1) of the then operative Motor Vehicle Accidents Act 84 of 1986 ("the Act") and had issued a token in respect of the bus under the provisions of the Act.

The appellants instituted separate actions for damages against NEG and Putco. They alleged the accident was due to negligence


on the part of the driver, alternatively, certain employees of Putco, alternatively, their joint negligence. The allegations of negligence were denied by NEG and Putco, and the appellants were put to the proof of their alleged damages.
The two actions were consolidated for the purposes of trial. It was agreed between the parties that the issue of liability would be determined separately from that of the quantum of each appellant's damages. The matter accordingly proceeded to trial on the merits only. The learned trial judge (CURLEWIS AJP), having heard the evidence of two expert witnesses, Messrs Keuler and Harre, and a number of passengers who had been on the bus, concluded that no negligence had been proved on the part of the driver or any other employees of Putco. He accordingly granted absolution from the instance with costs, but gave the appellants leave to appeal to this Court.

Of the four passengers who testified, all of whom regularly


travelled that route, three gave evidence that the driver, as far as they were concerned, was proceeding in a normal manner and at a normal speed at the time of the blow out. The remaining witness initially claimed that the driver was travelling at a "high speed"; later he upped this to a "very high speed". Despite being someone with driving experience, he was unable to give any estimate of speed. The trial judge appears to have accepted the evidence of the other witnesses in preference to his - a finding not challenged on appeal. Judged purely on their evidence there was nothing untoward in the manner in which the bus was being driven when the blow out occurred. No inference of negligence on the part of the driver relating to the blow out can therefore be drawn purely and simply from their evidence.

Knowledge of the fact that the accident was caused by the blow out precludes any application of the maxim res ipsa loquitur. That maxim is of application where the only known facts that bear


on the question of negligence consist of the occurrence itself, the cause of which is unknown, and the occurrence is of a kind which would not normally occur without negligence on the part of someone (Madyosi and Another v SA Eagle Insurance Co Ltd 1990(3) SA 442(A) at 445B-D). Thus the maxim can be invoked, and an inference of negligence drawn, where a vehicle leaves a road and overturns for no apparent or ascertainable reason; or where a ship collides with a stationary mooring buoy (cf Osborne Panama SA v Shell & BP South African Petroleum Refineries (Pty) Ltd and Others 1982(4) SA 890(A) at 897E-G); or where a bridge collapses or a railway line gives way and the cause cannot be established. In every case, however, including one where the maxim is applicable, the enquiry at the end of the case remains whether the plaintiff has discharged the onus resting upon him to prove the negligence averred against the defendant on a balance of probabilities (Arthur v Bezuidenhout and Mieny 1962(2) SA 566(A)


at 574B).
Mr Sceales, for the appellants, submitted that the maxim res ipsa loquitur was applicable to the blow out and that an inference of negligence could be drawn from the mere fact that the tyre burst. This submission is without merit. One cannot equate a burst tyre to the situations referred to above which might justify the maxim being invoked. A burst tyre is virtually an everyday occurrence. It can occur for a variety of reasons, some entirely unrelated to negligence. It is therefore not an occurrence of a kind that would not normally occur without negligence. But in any event, the two expert witnesses each put forward an explanation for the blow out. It will in due course be necessary to consider their respective explanations and, assuming their acceptability, to determine which is the more probable. Once a cause for the blow out has been established, the res ipsa loquitur maxim has no application. It then remains to be determined whether the driver was negligent in


relation to such cause.
One of the allegations made by the appellants was that the driver and certain other (unidentified) responsible employees had been negligent in failing to ensure that the tyres of the bus "were in a roadworthy and acceptable state" and that such failure had caused or contributed to the blow out. That it is incumbent on a bus company like Putco to ensure that the tyres on its vehicles used for the transportation of passengers are regularly inspected and kept in a roadworthy and safe condition goes without saying. The respondents called a witness, Mr Alpheus Marakala, who was employed by Putco as a tyre attendant. He testified that, according to the normal practice, the tyres of the bus involved in the accident had been checked by him the previous afternoon at the depot before its return to Denelton, where it remained overnight before setting off in the morning. This appears to have involved a check of the tyres' pressure, tread, valves and external appearance to ensure that it was


free of visible defects. Although the evidence of the witness was somewhat vague, there is no reason to doubt that he undertook a routine check of the bus's tyres. Whether the checks carried out were adequate is open to some doubt - cf. Barkway v South Wales Transport Co Ltd [1950] 1 ALL ER 392(HL) at 401B-E. However, it is not necessary to decide the point. The salvaged parts of the burst tyre were subsequently examined by Keuler and Harre. They were ad idem that on examination of the remains of the tyre they were unable to detect any defects in it which could have accounted for the blow out and would have been visible on proper prior inspection.

We do not know whether the tyres were ever inspected by the driver before he set out on the fateful journey. Assuming that it was his duty to do so (despite Putco's employment of tyre attendants), but that he failed to, and that the inspection carried out by the witness Marakala fell short of what can be considered


adequate, there is no evidence to establish that had a proper inspection been carried out a defect would have been observed of such a nature that a diligens paterfamilias would have taken steps to guard against the possibility of it causing harm. Whatever negligence there may have been on their part was "negligence in the air". It has not been shown to have been causally connected to the blow out. Blameworthy negligence on the part of the driver or Morakala, based on a failure to inspect the tyres, or a failure to inspect them properly, has therefore not been established.

The evidence does not justify a finding that a reasonably skilful driver could have prevented the bus from leaving the road and overturning after the blow out. Mr Sceales, in my view correctly, did not seriously contend to the contrary. There is evidence to the effect that after the blow out the driver simply threw up his hands and resigned himself to his fate, making no attempt to control the bus. This is highly improbable, and the evidence of


those passengers who say he struggled to control the bus is clearly preferable.
I come now to what I consider to be the crux of the present appeal. Has the cause of the blow out been established, and was there negligence on the part of the driver preceding and causally related to the blow out? This involves a consideration of the evidence of the two experts.

Harre, who testified on behalf of the respondents, was at the time of the trial employed by Firestone South Africa (Ply) Ltd as a quality assurance manager and co-ordinator of field engineering with expertise, inter alia, in the design and manufacturing of tyres. It is common cause that he was qualified to express an opinion on the cause of the blow out. As I have previously mentioned, he had visually examined what had been salvaged of the tyre after the accident. He was of the view that the blow out resulted from an impact fracture with consequent instantaneous deflation of the right


front tyre. This would have been caused by the tyre striking some substantially sized object on the road or hitting a pothole of significant proportions. The disintegrated state of what remained of the tyre, as appears from the photographs handed in as exhibits, he attributed to the fact that the tyre had run a distance without air pressure after the impact.

Keuler, who testified on behalf of the appellants, is a specialist in rubber technology with the South African Bureau of Standards where he has been employed since 1962. In his case, too, it was common cause that he was properly qualified to testify as an expert. He admitted that he could not be categorical about the cause of the blow out. His evidence was, however, to the effect that the blow out had occurred as a result of the intense build-up of heat due to flexing of the sidewalls consequent upon overloading or the gradual deflation of the tyre. As there is no suggestion of overloading in this case, the heat build-up would have


been due to gradual deflation. He testified that the ripping of the

sidewall, as appears from the photographs, was indicative of the bus
being driven while the tyre was under inflated. He further testified
that there was blueish discolouration of the tread rubber section of

the remains of the tyre, something normally associated with elevated

temperatures. He also expressed the view that the disintegrated

state of the tyre indicated that the tyre had been driven for a

considerable distance after failure, i e gradual deflation, had started

to occur.

With regard to whether the heat build-up and resultant

discolouration could have resulted after the blow out the following

passage appears in his evidence under cross-examination:

"MR PREIS: Or overloaded. I want to put this to you that if the tyre had burst and the tyre thereafter ran flat that this would have caused a build up of heat as well? — It would yes. The amount of heat which builds up depends entirely on the time that the tyre has been driven under inflated. If the tyre had burst then one would not expect it to run for a long distance. Obviously the bus would stop.


COURT: Not immediately. It is an enormously heavy thing. — The distance in which you can stop is certainly a lot less than what one would expect needed to have any heat build up in the tyre."

There followed, shortly thereafter, the following question and answer:

"Assuming that there was such blueish discoloration it could also have been caused as a result of the tyre bursting and
running flat in this matter? — It certainly has not been the experience that I had at the SABS with tyres that have been inspected that it could happen in such a short period of time."

Harre's opinion that the blow out was caused by an impact fracture is in my view not supported by the evidence or the probabilities. There is no evidence that any stone or similar object of sufficient size to have caused an impact fracture was seen on the road before the blow out, or found subsequently. Nor is there any evidence of the existence of a pothole of such dimensions that it could have resulted in an impact fracture. None of the passengers testified to having experienced any bump or jolt either immediately


preceding, or simultaneously with, the blow out. Nor was there any noticeable attempt by the driver to take any avoiding action. There is accordingly nothing to support a finding that "some extraordinary and unforseen episode had supervened" to cause the blow out (South British Insurance Co Ltd v Mkhize 1965(1) SA 206(A) at 207F-H).
Keuler's conclusion of the blow out being caused by heat build-up due to under inflation over a period of time is in my view both tenable (as conceded by Harre) and acceptable. There is no reason not to accept Keuler's evidence relating to the blueish discolouration and its cause. Harre opined that had the bus been driven for a number of kilometres with the tyre under inflated he would have expected a heat induced reversion of the rubber because of the severe heat build-up, which would have manifested itself in the rubber becoming sticky. Keuler conceded that there could have been a heat induced reversion of the rubber, but this could only be


established by chemical tests. It is common cause that no such tests were done. According to Keuler, the rubber would only become sticky where there was an advanced state of heat induced reversion. Harre fairly conceded that he was not an expert in rubber chemistry, which Keuler is. The absence of stickiness does not in my view detract from Keuler's evidence.

It is not possible from the evidence to determine precisely where the blow out occurred and what distance the bus travelled thereafter before it left the road and overturned. The effect of Keuler's evidence is that the blueish discolouration he observed is more likely to have been caused before the blow out than after. Once Harre's impact fracture theory is discarded there is no reason why Keuler's evidence should not be accepted, providing as it does a reason for the blow out which is entirely plausible.

In my view the most probable cause of the blow out was the fact that the bus proceeded for some distance with an under inflated


right front tyre resulting in a build-up of heat which led to the tyre disintegrating and eventually bursting. There could be a number of reasons for the under inflation - a puncture, a leaking valve or the loss of a valve are but some. The instances mentioned could have occurred without negligence on the part of anyone. Each would have caused a gradual deflation of the tyre over a period of time.

Should the deflation have been obvious to the driver before the blow out and could and should he have taken remedial action? The driver of a bus has a responsibility towards his passengers for their safety (Fredericks v Shield Insurance Co Ltd 1982(2) SA 423(A) at 428G). It is required of him to exercise skill in driving the bus commensurate with such responsibility and to react timeously to situations which could foreshadow harm to his passengers. It is perhaps appropriate to echo what was said by TROLLIP J in S v Stavast 1964(3) SA 617(T) at 623G-H:


"I think that having regard to the dreadful and almost daily toll that motor vehicular traffic exacts of human life and limb on our roads, the Court should be astute not to diminish but rather to raise the standard of care and precautions that should be taken by drivers in the interests of public safety."

(See too Union National South British Insurance Co Ltd v Victoria 1982(1) SA 444(A) at 458C.) A bus driver must be alive to any malfunctioning of his vehicle, or any significant change in its behaviour, which might signal possible danger. More particularly is this so when he is travelling on the open road at speeds in excess of those permissible within an urban area, as the possibility of harm increases in those circumstances. Once he notices that his vehicle is not functioning or behaving as it normally does, it is his duty to slow down or stop or take such remedial action as the circumstances permit to ascertain the cause of the problem and lessen any possibility of harm to his passengers.

The blow out involved the right front wheel. It is common knowledge that the front wheels of a vehicle are connected to and


controlled by the steering wheel. As a matter of probability one
would expect the progressive under inflation of a front tyre to affect
the steering capabilities of the vehicle at some stage. This would
be communicated to the driver via the steering wheel. In the
present instance this would probably have occurred some time
before the eventual blow out. This was recognised by Harre.
Asked during his evidence in chief if the partial deflation of a tyre
could increase its temperature and lead to damage he responded:
"But surely if the tyre was partially deflated there would be
such a drag on the steering that the driver would know that
he has a partially deflated tyre."

From this one may infer that a reasonably skilful bus driver would have realized that a front wheel was deflating. And as the deflation took place over a period, such realization should have come a sufficient time before the blow out to permit of some


successful remedial action being taken. The driver did not take any. On the evidence he proceeded at the same speed and in the same manner to the point of blow out. In my view he was, in the circumstances, negligent in some degree in a respect causally related to the blow out, and consequently the accident.

In the result I would have allowed the appeal with costs and have substituted an appropriate order for that of the court a. quo. As this is a minority judgment no point would be served in setting out the terms of such order.

At the commencement of the appeal Mr Sceales applied for orders condoning the late filing of (a) the appellants' notice of appeal: (b) their powers of attorney; (c) a proper record; as well as (d) an additional volume of the record. It is somewhat unusual, to say the least, to have so many applications for condonation. They redound to the discredit of the appellants' Pretoria attorneys of record. The respondents did not oppose the applications. Judgment


was reserved in respect of them subject to the appellants showing reasonable prospects of success. They were in the majority view not able to do so. The applications accordingly fall to be dismissed. The appellants should pay any wasted costs occasioned by applications (a) and (b). We raised with Mr Sceales the question whether the appellants' attorneys should not bear the wasted costs of applications (c) and (d). He did not, quite rightly, oppose the view that they should. The wasted costs occasioned by applications (c) and (d) should therefore be borne by the appellants' Pretoria attorneys de bonis propriis.


F H GROSSKOPF, JA - concurs