Could strict enforcement of speed limits be bad for safety?

12.00 | 28 October 2016 | | 9 comments

Strictly enforced speed limits could have a ‘detrimental impact on road safety’, according to new research from The University of Western Australia (UWA).

The study took place after the government in Queensland, Australia began issuing fines to motorists caught driving as little as 1km/h over the speed limit.

It concluded that when they are aware of strict limits, drivers dedicate more attention to monitoring their speed than detecting hazards.

The researchers used a driving simulator to test whether lowering speed enforcement thresholds would impact on a driver’s mental and visual abilities. 84 young adult participants drove under conditions where they could be fined for travelling one, six, or 11 km/h over a 50 km/h speed limit.

A ‘peripheral detection task’ was used to measure drivers’ mental and visual workload. They also filled out a questionnaire which asked how difficult or demanding they found the experience of driving under the different enforcement conditions.

The study says stricter speed limit enforcement led to drivers rating the experience as ‘more demanding’ with a ‘significant negative impact’ on peripheral vision and the ability to detect objects outside the driver’s immediate line of sight.

Dr Vanessa Bowden, lead researcher on the study, said: “Similar effects have been shown for individuals who drive while talking on a phone or operating their car’s stereo.

“Our overall finding was that stricter speed enforcement may impair a driver’s ability to detect hazards, especially those on the side of the road, because drivers are dedicating more attention to monitoring their speed.

“In reality the effects of strictly enforced speed limits could be even greater than in our study, with real-world drivers experiencing greater pressures to drive at or above the posted speed limit.”

The researchers plan to continue this line of study to see whether drivers are actually poorer at responding to hazards under conditions where speed limits are strictly enforced.




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    Clearly this was an abnormal situation in which the drivers were on a simulator. Also to be taken into account is their motive for maximising their speed. Speed limits are not a target but provide a ceiling to which you should not exceed. It is natural for there to be a variation in speed below that maximum in normal urban conditions.

    If anything the message should be that “driving at the speed limit takes more effort and introduces more distraction than normalising your speed below and allowing for inevitable fluctuations”. Hence its not about attitudes to compliance but attitudes to going as fast as possible without getting caught.

    Rod King, 20’s Plenty for US, Cheshire
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    Most of these comments appear to follow those of certain former BBC Top Gear Presenter.
    If you naturally drive to the speed limit shown in your vehicle then you will not generally exceed the speed limit due to the inaccuracy of speedometers. Many people push the boundaries and speed until they see a safety camera. If you fully concentrate on your driving then checking the speedo will not detract you from spotting other hazards.
    This is just another excuse for current poor driving standards.

    Keith Northampton
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    Driving at, or close to, the speed limit need not be a distraction that diverts attention away from the road environment. My Mercedes Benz, made in 2000, had a system that when engaged limited top speed to a pre-set level. It could be increased in 5mph increments and was simplicity itself to operate. Safety was not compromised, as acceleration above and beyond the set limit was made possible by disengaging the system with a firm push on the throttle.

    It was a real boon to have in a quiet car with little impression of speed, other than the speedometer itself. Quite why it is not universally fitted to modern cars is beyond me. I found it immensely useful to be able to drive without devoting any of my attention to the speedometer, knowing very well that I would not be exceeding the limit.

    David, Suffolk
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    It is going to be distracting to drive close to a speed, say 50kph and not exceed it by 1kph. Even cruise controls would fail that test. If I was asked to take that driving test I would use a targeted maximum of 40-45kph and would do that if the roads were enforced like that.

    If that suggestion was practiced then there would be little or no distraction and the conclusions of the test and indeed its premise would be that safety was not and would not be compromised by enforcement at +1kph.

    Further to this it is simply daft to consider such levels of enforcement and is wholly unnecessary. If you want most people to drive at a maximum of between 40-45kph then set a reasonably enforced limit of 40kph. If you want people to drive between 50-55kph then set a reasonably enforced limit of 50kph.

    It isn’t rocket science and if you use this practice in setting limits and enforcement you avoid the inevitable distraction of drivers driving to 50kph and failing to stay below 52kph.

    Alan Stringfellow, Newcastle
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    Gareth, a more logical conclusion could be that where rigorously enforced speed limits have to be considered to ameliorate the road safety problem, the road infrastructure is unfit for purpose and needs replacing. In my experience, the safest roads don’t need speed limits and they certainly don’t need speed limit enforcement.

    Charles, England
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    So I conclude from this study COULD the only safe roads be German Autobahns, where everyone is looking out for each other as there are no speed limits? Like heck they are!!

    This study feels to me a bit like baking the perfect sponge cake only to discover it tastes horrible on eating as the sugar has been left out?

    Gareth, Surrey
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    Yes is the answer, but we must be cautious because simulators may not accurately mirror real life. We therefore must not base policy on their results but they can be used to investigate why the real world is the way it is.

    The reported simulator results may go some way in establishing one of the reasons why reports have suggested that there may have been increases in serious crashes after speed cameras have been deployed (such as at sites across the whole of Thames Valley, London and Wales).

    We do now need to start using an evidence-led approach using RCT scientific trials and, once the effects of interventions are established, simulators could then become very useful to investigate why the interventions are having the effect they’re having.

    Dave Finney, Slough
    Agree (0) | Disagree (0)

    No – strict enforcement of speed limits isn’t bad for safety, but what is bad, is if drivers are not concentrating on the road ahead and spotting potential hazards which takes priority over looking at the speedo so, as it doesn’t say anywhere that we have to drive as close as possible to the posted speed limit, the solution is to drive comfortably below the limit with a margin that doesn’t require constantly looking at the speedo. Simple really.

    Were the participants reminded that they don’t have to drive up to the posted limit if they felt it would compromise their hazard perception? Our speed should be influenced by our need and ability to see and respond to hazards – not to go as fast as possible up to the limit and if you can manage it, try and spot a few hazards.

    Hugh Jones
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    I tend to agree with the headline, however I would like to read the actual study before I comment further but unfortunately it requires a purchase. I’m not THAT keen.

    Pat, Wales
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