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The Menace of Speed Limiters


Accidents involving Heavy Goods Vehicles, although rare, are often especially severe because of the vehicles' size and weight. Anything which can be done to reduce the number of accidents must, therefore, be a good thing. A piece of EEC legislation introduced over the last couple of years, whilst looking as if it will help to cut the number of HGV accidents, actually makes lorry accidents more likely, particularly on motorways, and is causing danger to lorry drivers and other road users alike.

Since 1 January 1994, most lorries, (and since 1 January 1996 this applies to nearly all lorries) have had their top speed automatically restricted to 56 mph. "And a good thing too!" I hear you say. "It will stop these maniacs doing 90 on the tail of cars". This is true as far as it goes, but, considering the wider implications, more dangers are caused than are removed. Let me explain.

Firstly, a brief word about how the speed limiter works. An electronic unit receives information, via the normal speedometer cable, on how fast the vehicle is traveling. When the speed reaches a pre-set figure, the unit operates an electro-mechanical device on the diesel injector pump, closing it down. This has the same effect as the driver lifting the accelerator pedal, although the pedal can be kept depressed, as the movement is taken out of the linkage at the injector pump. The unit is calibrated during the vehicle's annual test, and then you have a lorry that cannot exceed 56 mph.

To assess the effect this has on road safety, let us consider the various types of road on which the lorry can travel.

Firstly 30mph, densely populated areas. The speed limiter will make no difference here. An irresponsible driver can drive past a school at 8.45am at 55mph and the limiter will not do anything to stop him. The speed limiters contribution to safety: Nil. Its contribution to danger: Again nil.

Next, a single carriageway road, where the national speed limit for HGV's is 40mph. Our irresponsible driver can still exceed the limit by 40%, and the limiter will not take any action. The good driver, of course, will be way below the limited speed anyway, so it will not affect him either. Increase in safety: nil.

Now a dual carriageway, where the limit for HGV's is 50mph. The good driver still should feel no effect from his limiter. His speed would be below 56mph anyway, but our nutter is now only able to exceed the speed limit by 6mph, or 12%, as his limiter is doing its job. Some contribution to safety here although if the traffic pattern is such that he should only be doing 40, the contribution is small. Still, score one for the limiter.

Finally, we come to a motorway, where the legal limit for HGV's is 60mph. Our good driver wants to travel around at the legal limit. But wait! What's this? The speed limiter has taken over, and he can only travel at 56mph. No contribution to safety here. The limiter having failed to stop the nutter doing anything dangerous, has now stopped the responsible driver from doing something safe. Where is our nutter by the way? Oh, he's not on the motorway at all. He has decided that, as he cannot save time by "winding it up" on the motorway, he will take a short cut through some villages, where he can do 50mph, despite the limit being 30mph. So, no increase in safety, but extra danger being created on A-roads.

That, however, is only a small part of the problem. A more serious one is that, as all the lorries now peak at the same speed, they tend to bunch together on motorways, whereas before there were always faster lorries, and slower ones, and ones in between, so they tended to string out more. One problem caused by this bunching is that, with long lines of lorries travelling "nose to tail", in the event of an accident, you are now more likely to get a multiple pile-up than you were when they were more strung out. The other, perhaps more serious effect of this bunching is that you get a rolling road block travelling at 56mph in lanes one and two, which will force more cars out into lane three, causing a slow-down there as well. The snag is, on a fairly densely packed motorway, if you have got a block of traffic doing 56mph, a couple of miles behind that you have got traffic doing 30mph, and behind that you have got stationary traffic. (Think of the last time you were stopped on a motorway because of a wide load ahead travelling at 30mph!). Apart from the inconvenience, stationary traffic on motorways causes accidents. Add to this the fact that lorries can no longer take a run at gradients, which means their speed on long climbs will be even slower, and you have got some serious potential for accidents. No increase in safety, but a significant increase in danger.

The main problem caused by speed limiters, however, is boredom and fatigue amongst drivers, especially at night. Apart from the obvious fact that any journey where speed is lowered is going to take longer, driving a speed limited vehicle on a quiet motorway is mind-numbingly boring. Examination of a tachograph chart from a vehicle with a limiter will show that it maintains the speed at exactly 56mph, much more accurately than the driver ever could. This means that, particularly at night on a quiet motorway, your speed doesn't change at all, the engine note doesn't alter, and you don't have to overtake anything because nothing is going slower than you. All you have to do is sit there, foot flat to the floor, trying to keep the vehicle between the lines, at a speed that feels slow, for hour after hour. Couple this with the fact that motorway driving can be monotonous at the best of times, and that one's brain functions less well at night anyway, and there is only one logical result. You fall asleep. I know, I've done it. It's not pleasant to wake up a few seconds later in a different lane to the one you were in before. A surprisingly high proportion, (66%, according to one study) of fatal road accidents are caused by driver fatigue, and about 23% of motorway accidents are caused by drivers falling asleep. I have actually seen a 38 tonner coming towards me through the crash barrier on the M1, because, I am led to believe, the driver fell asleep, and it's not funny. How can anything that increases the risk of lorry drivers falling asleep at the wheel be a contribution to road safety?

"Roadcraft", the Police drivers manual, (published by HMSO) says "Driving for long periods of time in monotonous conditions such as..... at night or on a motorway reduces stimulation and promotes fatigue", and "Fatigue is most likely in conditions which are relatively unchanging". Driving at exactly 56mph with a speed limiter is the most monotonous driving you can do - the conditions are completely unchanging, and stimulation is reduced almost to zero. There is also a strong possibility that lorry drivers may be literally hypnotized at the wheel. Mr P J D Savage, Principal of the National College of Hypnosis and Psychotherapy, refers to "a phenomenon whereby a state similar to that of relaxation into hypnosis may occur whilst driving", and says "This would probably be most likely the case in motorway driving when all the senses would be so engaged as to promote a dangerous feeling of relaxed drowsiness, e.g. the driver is warm and comfortable, the view from his windscreen is monotonous and repetitive, as is the sound from his engine". This effect would be at its worst when driving with a speed limiter. The view from the windscreen and the sound of the engine are as monotonous and repetitive as they can be. All mental stimulus has been removed from the driver, along with the need to physically do anything, and has been replaced by the sensation of the motorway, with its lane markings, coming endlessly towards him, and the unchanging drone of the engine. This could well have the same effect as equipment used by some hypnotherapists to help induce hypnosis in patients. Commercially available self-hypnosis cassettes carry a prominent warning that they should not be listened to whilst driving, because of the obvious dangers of driving whilst under hypnosis. However, lorries are now fitted with devices which could almost have been designed to induce hypnosis in their drivers. This is making our motorways more dangerous, not safer.

Speed limiters, especially when set at too low a speed, have other, less obvious, effects on drivers. As the driver, when travelling at the limited speed, no longer has to control the vehicles speed himself, he no longer has the intimate contact with the vehicle through the accelerator pedal that drivers are used to. Control of the vehicles speed has been taken from him. The only thing he has any control of is the steering wheel, and on a motorway he doesn't really need to do anything with that. This produces a surprising feeling of detachment from the vehicle. When you drive with a limiter, you begin to feel like a passenger, not a driver. No matter how hard you try, your attention wanders, and if something happens which requires action by the driver, you may not react quickly enough. If you've got nothing to do, your mind wanders. This is quite frightening. I have noticed in the last few months, since limiters were introduced, that many drivers, especially of vehicles limited to 56, are adopting positions which one would normally only see in passengers. They are getting up to their limited speed, the limiter is taking over, and they are making themselves comfortable for a long and tedious journey. Many are leaning on their elbows on the steering wheel. These men are bored. Control of their vehicles has been taken from them and they become inattentive and distracted. Some appear to be almost asleep. Remember though, that they are still behind the wheel of 38 tonne lorries traveling at 56mph. They are behind the wheel, but they are not in control of their vehicles. Subconsciously they have become passengers, not drivers. Limiters are, in effect, causing lorries to be driven "without due care and attention". Surely this can't be a good thing?

Another effect that a limiter has on a driver is that, if he is trying to concentrate on driving, it is intensely frustrating when the limiter takes control away from him, and artificially and unnecessarily slows the vehicle down. Frustration leads to aggression, and the danger is that the driver may take out his aggression on vehicles passing him, or on other traffic when he leaves the motorway. Of course this shouldn't happen, but lorries are driven by men, not machines, and we ignore the human element at our peril.

Please do not get the idea that I am a cowboy driver who wants to be able to drive at high speed 24 hours a day intimidating car drivers. We've all seen them, and in my opinion the sooner these lunatics have their HGV licenses revoked the better. I am in favour of anything that makes the roads safer. I'm all for tachographs, and for the tightening of the hours' regulations. (How many of you know that the hours' regulations were relaxed in 1987, enabling drivers to drive and work for considerably longer than before?). I care enough about driving safety to have passed the Institute of Advanced Motorists test in an articulated lorry, and have spent ten years promoting advanced driving through the local Group. I genuinely believe, however, (and this is of course my own opinion, and not necessarily that of the IAM), that speed limiters are at best pointless, and at worst dangerous. They contribute practically nothing to road safety, and cause serious danger.

This law has been inflicted on us by the EC, (and we all know what a brilliant record they have got for sensible and constructive legislation!). According to the EC directive, limiters should be set to 53mph, but the British Government, clearly unhappy with that figure, has said that we should set ours to the top end of the so-called "operating tolerance" i.e. 56mph. Our Government was originally going to set them to the motorway speed limit for lorries, 60mph, but have been forced into accepting a lower setting, although they have opted for the highest speed allowed by the EC. As they seem, quite rightly, to believe that slower is not necessarily safer, surely they could accept a setting of at least 65mph, which would restore control to the drivers. Certainly drivers should still be prosecuted for going too fast, but "too fast" is a relative term. 30 can be too fast in some circumstances, and 65 can be acceptable in others. A Police officer (and for that matter most lorry drivers!) can tell the difference, but a speed limiter can't.

Incidentally, in 1992, per 100,000 of the population, we killed 8 people in road accidents. (In 1994 this had fallen to 6.7). The Germans killed 12, the French killed 17, and the Portuguese killed an amazing 34. In fact, of the 20 countries listed in the Government's annual statistics, no-one killed less than Great Britain. Why are we allowing countries with a far worse accident record than us to dictate our road safety policies?

There is no obvious reason why it was suddenly felt necessary to fit limiters in the first place, and why it was decided to set them below the motorway speed limit for this country. There has been no public clamour for limiters to be fitted, and no call for the motorway speed limit for lorries to be reduced. There is pressure for the limit for cars to be raised to 80mph, and the limit for caravans has been raised to 60mph. Why, then, should lorries be limited to 56mph?

A clue as to the real reason for fitting 56mph limiters comes from the Royal Commission on Environmental Pollution. They recommend that 56mph limiters be fitted to all vehicles over 7.5 tonnes, instead of the present 12 tonnes. This would suggest that limiters have been fitted, not in a misguided attempt to improve safety, but to reduce exhaust emissions. They can only do this if the driver surrenders control of his vehicle and drives "on the limiter" for long periods, which would explain why the limiters on lorries and coaches have been set below the motorway speed limits for those vehicles. This causes the fatigue and inattention problems described earlier. Whilst pollution control is a very worthwhile aim, it must not be done at the expense of safety. There are other measures which can be taken to reduce fuel consumption and exhaust emissions which do not cause danger. Diesel and carbon dioxide cannot be saved at the expense of peoples lives.

Recent years have seen improvements in vehicle design, standards of maintenance, and driving standards, and the introduction of such safety aids as anti-lock brakes and anti-jackknife devices. As we now have safer lorries, it seems illogical that the speed limit we have had for years should suddenly be deemed too high. It would appear more sensible to allow a higher speed for safer vehicles, not a lower one. A few years ago the IAM called for the limit for cars to be raised to 80mph on the grounds that vehicles have improved over the years. The same argument applies to lorries. Heavy Goods Vehicles already have the best safety record of all the vehicles on our roads (51 accidents per 100 million vehicle kilometres, compared to 94 for cars), and motorways are the safest roads in the country. It is also worth noting that, as learners in cars are not allowed on motorways, whereas HGV learners are, the only drivers who can have had any instruction in motorway driving are lorry drivers. It is perverse to fit devices which only affect the safest vehicles on the safest roads, and which then cause more danger, not less.

Speed limiters are a misguided and ill-considered measure, and when set at too low a speed are counter-productive. They have no effect on roads other than motorways, and their effect on motorways is almost entirely dangerous.

If we cannot do away with these devices, then perhaps an acceptable and safe compromise would be to increase their setting to 65mph, or 110kph. This will prevent lunatic drivers from racing about at 80mph, but will give responsible drivers the flexibility to do their jobs safely and efficiently. It will provide a "safety barrier" to prevent excessive speed by the dangerous minority, but it will give sensible drivers control of their vehicles again, and stop them from driving "on the limiter" for hours on end, which causes the problems mentioned previously. All that stands between a lorry and a serious accident is the alertness of the driver. Speed limiters dull that alertness to a dangerous degree.

Speed limiters are not the solution for making our roads safer. Sensible speed limits, properly enforced by the Police, are the only answer.

As these devices are fitted to more and more lorries, and set at too low a speed, then lorry drivers and car users are going to die on our motorways as a result. I understand that there are plans to ultimately reduce the speed setting to 50mph, which will make the situation even worse. Tankers carrying dangerous chemicals are apparently already being limited to 50, which means that the drivers with the most dangerous loads are those most likely to fall asleep. This is not something we should accept without a fight.

At the moment, it is only professional drivers, who have had to pass stringent tests, who are subject to speed limiters. (Coaches are fitted with limiters as well, set to 65mph, although their speed limit on motorways is 70mph). However, if we allow the regulators in Brussels, who want to control every aspect of our lives, to get away with this, then it won't be long before they fit a limiter to your car, probably set at 65mph or even 60mph. (Note: In 1997 they announced plans to limit cars to 62mph. - Cybertrucker.)

Please consider writing to your MP or the Transport Minister to protest at what I hope I have convinced you is a dangerous piece of legislation. Meanwhile, please be especially careful when driving on motorways. Look out for slow or stationary traffic in front of you, and sleeping lorry drivers coming towards you, all caused by the menace of speed limiters.


This article was published in "Police Review", 4 August 1996.


The first time I saw this lorry it was coming towards me through the crash barrier on the M1 motorway. No reason was found for the accident, and the assumption is that the driver fell asleep. Speed limiters make this more likely. I'll leave you to draw your own conclusions as to whether we really want speed limiters!