Road safety experts ignore UK sign problems

A recent report into the safety implications of variations in road signs across Europe has ignored problems caused by the UK’s continued use of imperial units.

In the last decade, 2 million Europeans lost their lives or suffered crippling injury on our roads. In purely financial terms, this costs a staggering 2% of European GDP.

In June 2011, two international road safety organisations jointly issued a consultation document, “Roads That Cars Can Read”, in which they forecast that thousands of European lives will be saved once the use of technologies such as in-car road sign recognition systems become as universal as today’s satnavs. The two organisations, the European Road Assessment Programme (EuroRAP), and EuroNCAP, are both dedicated to reducing the number of serious road accidents throughout Europe, and believe that these figures can be drastically reduced by improved road design, and the use of standardised road signs.

The report points out that, after over half a century of international treaties intended to standardise road signs worldwide, there remains “marked variation between countries even on the most common signs”. In addition to the safety implications of poor uniformity of road signs, these differences hinder the ability of future in-car road sign recognition systems to correctly identify signs. The report states that, “It is sure to be true that roads that can more easily be read by machines will be safer for road users generally too”.

As examples of how signs vary, the report shows 3 key signs as implemented in 5 different countries.

However, more obvious and serious differences between UK signs and those of all other European countries have been ignored. The signs below show speed limits as seen in the UK, France and Germany.

Whilst here too there is a lack of uniformity in the use of type faces and the thickness of the outer red circle, there is a far more important difference between these signs. Although superficially similar, the UK sign is alone in not having the same meaning. It prescribes a completely different speed limit from the other signs.

The report also erroneously asserts that “all countries appear to follow the principles of the UNECE protocol agreed in 1949 and revised in 1968”, whereas in fact UK vehicle width, height and length restriction signs are non-compliant because they do not use the units of measurement specified in the protocol, which are metres only.

Section C, II, 1(e) of Annex 1 of the Vienna Convention on Road Signs and Signals specifies the units for vehicle restriction signs:


The publication of “Roads That Cars Can Read” comes only weeks after a decision by Philip Hammond, the Secretary of State for Transport, to ignore the outcome of an earlier Department for Transport consultation which had recommended that all width and height restriction signs be shown in metres in addition to feet and inches.


The Vienna Convention on Road Signs and Signals 1968 is an international treaty designed to increase road safety and aid international road traffic by standardising the signing system in use internationally. Its signatories include the UK and more than 50 other countries worldwide.

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56 Responses to Road safety experts ignore UK sign problems

  1. John Steele says:

    @Wild Bill
    Good detective work. If you move closer, the interior bridge is marked as an arch with the yellow and black border. However, it is so deep in the shadows it may not be apparent to a driver out in the sun.
    (You have to move view into those shadows so the camera exposure adjusts)

    As an American used to LHD vehicles, I note than only half the chord line is marked (from center to chord). In a LHD vehicle (and this may affect foreign lorries), it would be a little difficult to align yourself with the chord markings. I note on the far side, the bridge has suffered a visible strike exactly where I think the missing half of the chord line marking should be. My understanding from browsing the traffic signs manual was that the full chord over which the vertical clearance applies should be marked.

    The markings may or may not be minimally compliant with the law, but when there is a repeated problem, the best practice that the law allows seems more likely to help than being minimally compliant. The local council should be looking at how to improve the markings.

  2. Ezra Steinberg says:

    The point previously made about consistent and universal signage is key here. Any driver, whether English, Welsh, Scottish, Irish, or from the Continent should be able to count on what to expect in terms of signage and warning when the approach a bridge or underpass. This means dual signage (Imperial and metric) everywhere.

  3. philh says:

    I must admit that I find para 7.8 of the traffice signs manual interesting:

    "Metric heights may be shown in addition to
    imperial heights at any bridge. This is recommended
    for all bridges on main routes and on roads used
    frequently by foreign drivers. ..."

    I think one can draw the conclusion from this that the Department for Transport do acknowledge that not all drivers understand imperial!

    Thank you Wild Bill for drawing attention to that part of the document.

  4. Ezra Steinberg says:

    Since the traffic signs manual mentions the option of showing metric heights at any bridge, does it have anything to say about showing metric widths or metric lengths?

    For example, a bridge that is located over a low point between two hills should (I would imagine) have posted a length restriction. Similarly, narrow one-lane bridges would seem logically to need a width restriction posted. The reasoning behind posting metric heights should call for metric signage in those cases as well --- I'm just wondering if the traffic signs manual mentions those situations.

  5. Wild Bill says:

    Thank you to just about everyone for your appreciative comments recently! In answer to John Steele's comment about the chord line, from my reading of the Traffic Signs Manual (TSM) then that chord line should reach from side to side of the the centre. Not just to the one side as happens here.

    To Philh: I never thought there was doubt in the DfT's mind about the need for metric signage, that's why metric height has been an option since (according to wikipedia) TSRGD 1993, and the metric width option has been there since TSRGD 2002. The problem in this case isn't the DfT (for a change!), this time it's the local authority. They are the ones who get to choose whether the available metric options get used or not and here they seem to be stubbornly refusing to take up on it.

    To Ezra: unless I'm mistaken,, there is no legal option for a metric length limit to be displayed on any sign in the UK.

    That said, I do believe that a local authority can get permission from the DfT for any sign saying any thing - they just have to get it cleared on a case-by-case basis. But that's a PITA for them, and so the usual situation is that only signs meeting the current TSRGD ever get put up, because they need no special authority for any of those. So you could have a metric length sign by special arrangement.... I don't think I've ever seen a length-limit sign "in the wild" though.

  6. Ronnie Cohen says:

    The recent DfT decision is irrational, inexplicable and incomprehensible. The response to their own consultation about mandatory dual signs for bridges showed a net saving of £1.8 million over ten years and strong support for the change from many stakeholders. They have still not explained why they dropped this proposal nor are they interested in adopting the Vienna Convention for height and width restriction signs.

    The Department for Transport recommends that local authorities use metres on restriction signs but despite the problems with the grossly disproportionate bridge strikes by foreign lorries, it is a scandal that local authorities are still putting up imperial-only restriction signs with the endorsement of the DfT. Had the DfT made it mandatory to use metres instead of optional when metres were first introduced on restriction signs, it would have cost no more money and we would not have this problem with the excessive number of bridge strikes by foreign lorries.


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