On single carriageway roads a 40 mph speed limit applies to Heavy Goods Vehicles (HGV)
In a deadly and foolhardy move, they are apparently increasing enforcement of this
strange and unnecessary speed limit.


On single carriageway roads in the UK an anachronistic 40 mph national speed limit applies to goods vehicles over 7.5 tonnes. Fortunately the limit has been widely ignored. While we're confident that goods vehicle drivers are fully aware of the limit most other road users don't even know that the limit exists. It's easily confirmed by the on-line version of the Highway Code. (click here)

Vehicle Speeds in Great Britain (click here) reports: "On single carriageways 76% of articulated HGVs exceeded their 40 mph limit, and 28% were travelling faster than 50 mph." But these figures refer only to sample sites. At the next sample site, on average 76% will be exceeding the limit, but it won't be the same 76%. In this way, many more than 76% of HGV drivers exceed the single carriageway national speed limit.

Indeed, on the evidence of our own experience, it is quite rare to encounter an HGV observing its 40 mph speed limit, and we suspect that other factors at the sample sites led to the figure of 76%. We'd estimate the percentage to be well over 95% in truly free flowing conditions on suitably open roads.

Recently we've been hearing increasing numbers of reports of enforcement of this strange and unnecessary speed limit. HGV drivers, who need their driving licences to earn their living, are especially affected by such activity. Unsurprisingly some of them are deciding to obey the limit in spite of the consequences. But what are the consequences?

Signs like this have been appearing on "A" roads in Scotland

New. We have had reports of drivers of other vehicles misunderstanding these non-standard signs and driving at 40mph. Perhaps it would not be unreasonable for a driver to assume that the sign referred to both a speed limit and a weight limit. We abhor any sign that misleads.

Danger from increased enforcement

Car drivers and lighter vehicles are quite reasonably allowed to travel at 60 mph on the roads in question. But on our congested roads these days good safe overtaking opportunities are not terribly frequent.

If we allow increased enforcement of the 40 mph speed limit for HGVs then an obvious consequence will be increased frustration for following traffic. This frustration will clearly lead directly to more risky overtaking and to more deaths and serious injuries. 

Obviously the immediate responsibility for an overtaking accident lies with the person executing the overtaking manoeuvre, but "innocent" people are almost always caught up in such accidents. The person overtaking and causing the accident is likely to be guilty of dangerous driving, but that's no real consolation to the innocent victims or their families.

Every accident investigator knows that frustration causes accidents.

It really does not help that we fail to train drivers in safe overtaking; it's potentially one of the most dangerous possible manoeuvres, yet drivers are expected to learn how best to do it all by themselves.

However, it might be argued that safety could be improved by reducing the speeds of HGVs on single carriageway roads. If there was any evidence at all to suggest that HGVs typically slam into other vehicles at free travelling speeds it would have to be considered carefully. But such accidents are rare, not least because HGV drivers are better trained.

Economic effects of increased enforcement

Suppose that increased enforcement reduced average speeds of HGVs on A roads by 5%. Immediately we'd need 5% more HGVs and 5% more drivers to do the same amount of work in the same time on the same roads.  We'd have 5% more HGV traffic on the affected roads, increasing congestion.

We'd need a good sound safety argument before these effects were worth tolerating.

But it isn't just HGV travel times which will be affected. If this limit is further enforced HGV drivers will be recruited as "rolling road blocks" to clog up our roads. All single carriageway road travel will be slowed.

An HGV driver's view

The trigger for this page was email correspondence from an HGV driver called Dave. Dave wrote:

"Recently, the number of company drivers being caught speeding has increased dramatically. On certain stretches of road where the police have been particularly active, these company drivers have decided to drive at the 40 mph blanket speed limit (for the single carriageway roads). Soon, every car driver will dread a journey on the type of single carriageway road that is difficult to overtake on. This is because they will be staring into the back of slow moving trucks for many, many miles. It is surprisingly relaxing to set the cruise control of a heavy articulated truck at the 40 mph limit. This is because the road ahead usually becomes empty of traffic, and when you arrive at the next normally busy junction or roundabout, you arrive first in the queue. :-)) It is important not to look behind for too long though, because the view of a queue of traffic stretching out to the horizon behind you can initiate a guilt complex.

Last Wednesday, while driving in "slow motion" mode [i.e. keeping to the 40 mph single carriageway speed limit for HGVs] between Warminster and Salisbury, after a very short three lane section, the road reverted to two lanes and a double white line for good measure. I was surprised that a car overtook me on the first 60 feet of double white line, and then totally amazed when white van man overtook both of us! He almost piled into the front of another speeding white van man hurtling around the bend from the other direction!"

By the way, what does LGV mean?

LGV is the new preferred term for a "Large Goods Vehicle" and replaces the term HGV (Heavy Goods Vehicle) in much modern literature and legislation. Confusingly, LGV has been previously used to describe "Light Goods Vehicle", and remains so used in some official literature. Accordingly if you use the new preferred term, there's a risk of having to explain yourself, which is exactly why we didn't use it. 

SafeSpeed comments:

The single carriageway national speed limit of 40 mph for HGVs is completely unnecessary and actually dangerous. HGV drivers have been ignoring it widely for years, and rightly so. The police too have very sensibly ignored this speed limit for many years and with equally good reasons.

In many cases it is safe and reasonable for HGV drivers to travel at their top limited speed of 56 mph on our better single carriageway A roads. Indeed, this is exactly what hundreds of thousands of safe and responsible HGV drivers have been doing daily for years.

This 40 mph limit certainly must not be further enforced, and instead should be urgently revised upwards to at least 50 mph. While we're about it we might as well raise the HGV dual carriageway limit to 60 mph too.

Obviously this is a serious matter, and we decided to write to the Minister of Transport about it. Our letter is below, and we will publish any reply on this page when it arrives.

26th May 2003
The Rt Hon Alistair Darling MP
Great Minster House
76 Marsham Street
London SW1P 4DR

Dear Rt Hon Darling

40 mph national speed limit for large goods vehicles on single carriageways

I am receiving reports of increased enforcement operations against LGV operators exceeding the anachronistic 40mph national speed limit on single carriageway roads. Naturally drivers of such vehicles require their driving licence to earn a living, and they will respond readily to such a move by slowing down to 40mph.

I am sure you are aware that, for many years, both the Police and the majority of our well-trained and responsible LGV drivers have widely, properly and safely ignored this particular speed limit.

In all the research I've been able to discover, I have found no evidence that increased enforcement will be beneficial to road safety or road efficiency and I request that you conduct a through review of the available evidence urgently. Indeed I believe that there are excellent reasons for expecting the increase in enforcement to increase road dangers and it will obviously reduce transport efficiency.

In particular, at 40mph LGVs will act as rolling roadblocks restricting traffic flow and increasing frustration in following drivers. Any accident investigator will immediately be able to confirm that overtaking triggered by frustration is very dangerous and claims many lives each year. Naturally we should also be concerned about the innocent drivers who happen to be travelling in the opposite direction.

An adequate reply would include either:

a) References to research that shows clearly and incontrovertibly that increased enforcement will save more lives than it causes to be lost, or
b) A simple clear statement about exactly what you are doing to prevent overzealous enforcement of this anachronistic speed limit, or
c) A simple clear statement about what you will be doing to repeal the aforementioned speed limit.
I look forward to hearing from you. I intend to publish your reply to the Safe Speed web site.

Yours sincerely

Paul Smith

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Created 24/05/2003. Last update 7/03/2004