Overtaking Questions & Competencies


Two Dead after driver passes on yellow lines:
NZ Herald, 08/ 10/ 2007: [or Post Scripts< BoP-Times, 26/ 12/ 2011 >below]

To illustrate the stupidity and incompetence of those who attempt to argue that (high) speed limiters might be dangerous in some (overtaking) situations, is to example the opposite in terms of a statistical illustration, demonstrated by the tragedy described in the NZ Herald 08 - 10 - 2007.

In this ‘head-on’ crash, a young male driver has overtaken on yellow lines [on Bawden Rd, Dairy Flat, Auckland, NZ.]  and has caused the death of himself and Lois Marjorie Booth, a much loved 70 year old grandmother.  The crash has also left her daughter, Linda Gedye, seriously injured.

Without duplicating a lot of previously described explanations concerning the relationship between overtaking competencies and a drivers ability to safely utilise higher (but not excessive) speeds, it is pertinent to simply repeat the main safety consideration. This is not one of evaluating any percentages relating to experienced  drivers knowing when it is safe to use a speed of perhaps 130km/h to accomplish said manoeuvre - it is the PREDICTABILITY that from time-to-time inexperienced drivers will cause fatalities - by attempting to use some of the 180km/h ESL activation - on their (unrestricted) vehicle/s.
. . . Read also; article, Overtaking Competencies ANALYSED >>

Pending further investigations by the Serious Crash Unit (SCU) it is nonetheless highly probable that the driver of the overtaking vehicle [a higher performance type saloon] would have been deliberately utilising an excessive speed - of perhaps 150km/h - in an immature attempt to accomplish the manoeuvre within the ridiculously shortened road space available.

Question, what would have happened in this manoeuvre, had the offending vehicle being restricted to 120km/h?
In a worst case scenario, supposing that the offending driver had still attempted the manoeuvre -regardless of the imprudence and recklessness involved - he may thus have attained a speed of 119km/h. At this (illegal) but slower speed, he would have gained the realisation that he was rapidly closing on another vehicle, in a head-to-head situation, with an earlier “time” advantage.

This “time advantage” may have thus provided both drivers with enough time to perform evasive actions - perhaps crashing into a ditch instead of an oncoming vehicle!
Additionally, they may also have had a (small) chance to brake, and hence reduce some of the kinetic energy at point of impact - resulting perhaps in injury instead of fatality!

Footnote: There is no inherent safety problem from the “acceleration” performance of this (at fault) vehicle.  Provided that such vehicles were restricted to a sensible top speed, the greater acceleration they possess would not increase the (fatality producing) kinetic energy dissipation at the point of impact.
In other words, the question concerning whether top-speed limiters could pose a danger in some situations is made redundant by the fact that any deleterious statistic would be completely outweighed and mitigated by the benefits associated with crashes prevented.
There are those who might argue that the statistics don't show the incidents that didn't result in a recorded crash - as a result of where a driver has used a speed of 135km/h to pass another vehicle. Perhaps they might direct their attention to the loved ones of victims such as the late Annie Borgman who was killed as a result of a reckless attempt to overtake; SH.1 -15/ 01/ 2006 near Wellsford.
I.e. As well as countless others involved in similar fatal scenarios, this crash occurred when an incompetent driver (Sayed-Ali Sarwari) has attempted an overtake manoeuvre but his speed attained was evidently well below that of a sensible ESL activation.

Question; notwithstanding his speed being only perhaps 90km/h at point of loss of control, was the driver of this Mercedes car --and who had been witnessed overtaking inappropriately shortly prior to the crash - RELYING on the knowledge that his vehicle could achieve 165km/h, to help him complete his manoeuvres safely?

Whatever the answer, the result of his driving on that day was fatal for HIMSELF and Mrs Borgman!!
IN OTHER WORDS, some of the "direct" benefits that would be achieved by the widespread implementation of top-speed ESL would not have to necessarily be calculated against incidents that "didn't actually happen" [i.e. calculating %<crashes that would have occurred had vehicles not been restricted].  Niether would the benefits be confined to crashes avoided where an excessive speed would (otherwise) have been used. The tragic death of Annie Borgman demonstrates that ESL regulation would prevent some fatal crashes even because the driver has Not KNOWN or USED a high speed, just that they were going to use one to overtake safely??

Post script>... example, to the above cited fatality (though there have been countless similar illustrations) is the avoidable tragedy on Xmas day 2011 at Tauranga, NZ, that has killed (sisters) Brooklyn  and Merepeka Morehu-Clark. The driver of the car they were passengers in has been charged with manslaughter because (evidently) he has overtaken using excessive speed - that is, he attempted one of those (safe??) bursts of high speed that some incompetent spokespeople, during the mid 1990s, have argued were necessary?? from time to time, "to get you out of trouble"??
Well done ! to those so-called-advisors? - who appeared on the TV-One-Paul-Holmes/current/Affairs.
[www-Merepeka Morehu-Clark, 14 and Brookly Morehu-Clark, aged 13, of Tauranga, died when the car they were travelling in collided with another, but it appears that high speed was a major contributing factor in the first instance. Would modern speed limiter restriction have prevented this tragedy!]  Two young lives wasted, because politicians (other than those in www-Sweden...possibly) won't implement the obvious ESL remedy.

Less Time Over The Line... & complementary information with other websites:
An ANCAP endorsed web article states; "...there are myths and misunderstandings about the need for reserve power and an excessive speed when overtaking.... in nearly all circumstances it would have been safer to brake than accelerate..." < Transport-Resrch-International-docmt:/ - -page 4 >.

There are at least two other websites that have excellent and in depth articles instructing on the competencies of overtaking.  One is named "Safe Overtaking & Road Safety" <www.arivealive.co.ZA > and deals with the actual procedures involved rather than the statistical consequences of getting procedure wrong - as we do in our article Overtaking Analysed.
Another excellent article is "How to Overtake"-//www.advnced-drivg-UK...> Despite having a similar number of spelling and grammatical errors to this website, the article fully complements the position regarding competencies required - as in Overtaking Analysed.
Yet another is<
>. Unfortunately, these above cited links, fail to explain that a simple way to ensure safer overtaking would be to sensibly utilise the embedded speed limiter functions, available in late model vehicles.

Overtaking "Time-segments" -re; www-Plowden & Hillman -(1984) re;page 26 > ...point out the main effect of a speed limiter is that "The driver of a high performance vehicle would no longer perform certain manoeuvres which he [Sic] now regards as safe".   Analysis of relevant data provided in the early nineties, by Lay(1991) and Troutbeck (1984) suggests that a typical passing manoeuvre on a rural road will result in a speed about 13km/h faster than the vehicle being overtaken, and a "time factor" of about 12.5s.    Refer also; About Us- page 7 .
Fildes & Lee (1993) also provide detailed review of (then) research into involvement of excessive speed in serious crashes...

...additional information on topic pending...>  Refer also: "Acceleration Versus speed"

Combined Speed Factors & associated statistics - for top speed [ESL] restrictions

With a degree of shallow analysis / appraisal, some readers may conclude that the majority of very serious crashes are the result of head-on type incidents - and therefore the combined speed factor involved, invalidates the significance of limiting top speeds.
Though correct in terms of supporting an argument for deprecating the benefits, associated with the [lesser percentage of] crashes that involve a single vehicle impacting with a stationary object, it should nonetheless be emphasized that the nine to 14 percent of high-speed “single vehicle” incidents (nonetheless) continue to account for about 18% of all road fatalities.

A possible secondary aspect, that could well provide an addition to this [18 percent] statistical value - is that there could be a previously unrecognized cause of ‘head-on’ crashes - that arises from an “inducement factor”. This inducement would relate to the "knowledge by the driver" that he/ she is able to use a very high speed [albeit only briefly] to conduct a given manoeuvre.
As explained in the [more substantive] article Overtaking Scenario Competencies and in some other articles in this website, the described inducement to use a dangerous speed (type of) scenario, may be what has provided the ‘trigger’ for many an unwary driver to have become the at fault party - in some of the (needless) head-on tragedies, that are witnessed at times, on the notorious highway black-spots.

If this “Inducement Factor was able to be proven to be the overriding psychological trigger involved when a less experienced driver made an imprudent decision to overtake - refer to: “Overtaking Competencies” - then the 25 percent reduction in (fatal & injury) crash trauma applicable to a restriction of top speeds, may therefore need to be calculated at a much higher statistical benefit, than 25 percent.

For example, this [greater percentage] would need to be proportionate with the fact that more than 50% of fatalities will occur in ‘head-on’ crashes.  Refer also; complementary LINK/<-ANCAP-suggests-120km/h-speed-limiters... >.

Combined Speeds & the Mathematical Statistics . . .

To summarise: It is widely recognised that as much as 50 percent of fatalities and / or serious injury crashes involve head-on impacts.
These impacts will occur at varying degrees’ [angles] of opposing directions.

Nonetheless, where they generally arise from an impact with a vehicle from the opposing direction, they are termed “head-on” - and can also be "two-car".

These incidents therefore, will usually produce the “combined speed” effect – that we are all acutely aware of in terms of potential for severity, in respect that the energy, of both the vehicles, is combined.
This effect (then) obviously renders the potential of a speed limiter, mostly redundant. This is because the two respective speeds of the vehicles means that if at the point of actual impact, one vehicle is travelling at 114km/h, and the other at 75km/h, the combined speed total will be 189km/h.

It is therefore obvious, that in this scenario neither vehicle would have been rendered any safer, by a speed restriction of 120km/h.
However, what must be remembered is that many cross-centre-line incidents will have - as their initiating aspect - a speed that is too excessive in the first instance, such as 130km/h or greater.

These types of speeds [if used by only one of the vehicles involved] may then result in that vehicle crossing the centre line.
A typical example of this type of incident - and that evidently did not involve an attempt to overtake using high speeds - was demonstrated on the Waitohi-Temuka highway, South Island New Zealand, January 2006.
In that tragedy three people died, evidently because one vehicle was travelling at about 130km/h when the driver simply lost control - and crossed into the path of the oncoming vehicle - (killing a much loved Grandmother).

The actual IMPACT speed of the offending vehicle in this incident may have reduced to 105km/h - at the point of impact - but this nonetheless produced enough energy dissipation to cause fatalities - through the combined speed effect.

Notwithstanding that the combined speed factor will mean that a high percentage of serious impact crashes could still occur when vehicles were restricted to a top speed of 120km/h, LTNZ statistics show that about 18 percent of serious impact crashes would in fact be prevented - resulting in at least a 25% reduction  in associated trauma; I.e. fatal & injury.    [25%= 68 fewer fatalities in 2005- for NZ roads.]

With regard to this (trauma percentage) reduction, it is important to appreciate that it would involve and lessen the more serious injury and deaths - that are having traumatic impacts on unsuspecting families.

Because many cross-centre-line incidents [head-on crashes] have speeds above 130km/h as their initiating factor, it is patently obvious that a restriction to about 120km/h’ would prevent many incidents from occurring in the first instance - and reduce the impact severity' of any that did take place.

Note: The argument, that having vehicles restricted to a specified speed might somehow exacerbate a “scenario” where an overtaking vehicle becomes trapped - in the face of oncoming traffic - is completely flawed when analysed concerning the statistics associated with these types of scenarios.   This is because - to cite just one obvious aspect - drivers are already making judgment errors that result in them becoming "trapped" as it were; and in some of these instances - because their speed is exceptionally high - they are having serious crashes (in any case -re above) notwithstanding the current 180km/h restriction of their vehicles.
This is apptly illistrated in the Bawden Rd crash cited at top of this article.