Could London bus accident have been prevented?

This weekend we heard the sad news that 26 people were injured when a double-deck bus hit a low bridge in Tottenham, north London. But could this accident have been prevented?

The driver of the bus evidently ignored the height restriction signs and failed to stop before hitting the railway bridge in St Loy’s Road, Tottenham. We do not know why the driver failed to take heed of the signs; but we can look at whether the signs, the responsibility of Haringey Council, were as good as they could be.

As photographs of the accident illustrate, the bridge was signed, with a height restriction of 13 feet 3 inches; the signs have been in place for several years, and therefore do meet the minimum legal standard. But do they meet the recommended standard? Clearly, they do not.

Since 1994, it has been recommended by the government that low bridges should be signposted not only in imperial units, but also in metres; the Department for Transport has concluded that the inclusion of metres is safer, and this is supported by an overwhelming majority of highway authorities. This government guidance was strengthened in subsequent releases of the Traffic Signs Manual, and the current law permits the erection only of dual-unit signs, which include metres, although no deadline was set for the removal of pre-existing imperial-only signs.

Therefore while the signs in St Loy’s Road were legal, they certainly fell short of the recommended standards and guidance, and it will be interesting to know if this is taken into account.

Haringey Council cannot claim to be unaware of the sign standards.  In 2013, UKMA conducted a survey of highway authorities across the UK, which fed into a report in 2014, and Haringey accepted that metres should be added to such signs, stating in September 2013:

“The Council is aware that the Traffic Signs Manual recommends that all warning and regulatory signs displaying height, width and length restrictions, should show the restriction dimensions in metres as well as imperial units. We are currently reviewing our bridge height and width restriction signs to ensure that they are clearly visible and provide information in metric and imperial units. The review will identify any signage requiring attention.” 

We applauded the Council’s recognition of this problem, so were disturbed to learn that 26 people have now been injured in an accident at a site where imperial-only signs are still in place, three years after the Council acknowledged that the signs was substandard. Although we cannot say if the units were a factor in this particular accident, it does highlight the need to take very seriously the signing of such obstructions over the highway, and to do everything possible to follow the latest guidance to make the signage as good as it can be.

UKMA hopes that Haringey, and all other highway authorities in the UK, will now redouble their efforts to make our roads safer and bring their low bridge signing up to modern standards, which includes showing height limits in metres on all such signs.

29 thoughts on “Could London bus accident have been prevented?”

  1. There is a metric/imperial warning sign at the start of the road which the bus must have already passed before reaching the bridge, so the metric vs. imperial argument clearly has no validity in this case. And bridge strikes aren’t just a problem in the UK, they happen in metric-only countries too – they are a problem related to ancient infrastructure rather than signage, and the the UK’s roads are amongst the very safest in the world. So this appears to me to be yet another unfounded, opportunistic attack motivated by the desire to metricate at all costs (even if it means making the roads more dangerous) rather than the desire to make the roads safer.


  2. It perplexes me as to why anyone would ‘Dislike’ an article on making the roads safer.


  3. @ Charlie P
    I don’t know about the sign at the start of the road but the sign on the bridge was clearly imperial only. That shows a blatant disregard of public safety by the responsible authorities in my opinion. Surely anyone can see that the safer option is to give a height restriction warning in units of measurement commonly taught in schools for over fifty years ( the official measurement system of the UK) rather than one given in an antique method of measurement only fully understood by people over fifty or sixty years of age. Bus companies tend not to hire OAPs to drive their vehicles.


  4. To know for sure if signs were the issue, the driver would have to give an honest account. Now, if the driver is a metric opposer, he may claim he doesn’t know metres and would only rely on the feet and inches. We then assume that he has a strong feel for feet and inches. But, what if he really doesn’t? What if he thinks 13 feet and 3 inches (4.3 m) is much higher than it really is or despite his claim he can’t do the calculation in his head quick enough to know if he has sufficient room to spare.

    Being a private bus explains why the driver would make such a mistake. If it had been a seasoned public bus driver, there would be no excuse.


  5. Bridge strikes do happen in all countries, whatever the signs say. Nevertheless, the fact that foreign lorries have a higher strike rate than UK lorries points to the need for dual signage.

    It is not possible to know whether this particular bridge strike could have been avoided if the sign gave both metres and feet and inches. However, the general point remains true, as foreign drivers are over-represented in these accidents..

    I have read Charlie P’s comment above and I feel that he seems to be motivated by a desire to resist partial metrication at all costs, even though there is clear evidence that dual signage would be safer. This definitely seems to be putting ideology above road safety.


  6. Some dual marked signs are quite small, making it difficult to pick out the numbers in the short amount of time available before passing the sign. This potentially could be very confusing. Time to ditch redundant and outmoded imperial units and provide clear, unambiguous metric-only signs that everybody understands (if they don’t, then it’s only because they choose to not understand, which is no excuse).


  7. I neither voted a “like” or dislike;” however, the article is weak in that it does not really consider true root cause in any way, it simply force-fits the problem into a pre-conceived solution.

    Is the driver an immigrant and/or foreign educated vs being educated in the UK? It is likely he does not understand Imperial? The article assumes so with no evidence.

    A chartered bus is much more likely to be on an unfamiliar route than regular city bus. What are the obligations of the driver and the company to determine the route is safe before taking it. Is the height of the bus posted near the driver for ready reference (I know this is required for a truck, but I don’t know for a bus)? If it is posted, in what units? Is there a registry of height and width restrictions in the UK that the driver or company can check the proposed route against? Does the driver understand his obligation to ensure the bus has adequate clearance at every overpass? Was the driver sober (it was a party bus)?

    UKMA is unlikely to be in a position to investigate all these questions, but the assumption that metric signage will largely fix the problem only makes sense if there is some evidence that the majority of drivers responsible for bridge strikes do not understand the height of their vehicles and/or the bridge due to lack of understanding of the units used.

    I am not opposed to metrication and I believe height restrictions in a single unit, meters, is easier to compare quickly to a vehicle height placard rather than feet and inches, where two comparisons are necessary. However, I believe it is necessary to consider other possible factors and not simply jump to a conclusion.


  8. There’s no evidence of signs or imperial / metric being an issue, more like human error raised it’s head again.

    In general, people are rubbish at estimating heights / lengths etc, couple this with distractions / change of route etc and this thing will happen,

    Perhaps there’s a gap in the market for a sensor to alert drivers of vehicles if they are going to enter a space which can’t accommodate their vehicle

    (Editor. … as installed on the southern approach to the Blackwall Tunnel, London, SE10?)


  9. @ Daniel Jackson:

    A public transport bus driver, seasoned or otherwise, would be driving on a pre-designated route along which it is known that there are no height or width restriction hazards. The only time the driver would depart from that route would be if there was a diversion, in which case the diversion route would also have to be appropriate for the bus heights concerned. But none of this applies to private hire of buses: while the destination would be pre-arranged (there usually is one), the route would not necessarily be and the hirer or a guest might well ask the driver to take a particular route of choice. This is where the trouble starts if the driver is not familiar with the area he is driving in. Or he may indeed be a foreign driver totally unfamiliar with non-metric signs. The ‘opposition’ to metrication claim the foreigners should learn imperial, but that is a stupid attitude to take in a country which has taught metric in school now for over forty years but does still not ‘practice what it teaches’.


  10. @Michael,

    I really don’t see the need for dual signage, just metric only. But because of the media reaction to metric only, the only way to progress is with baby steps. Get everything over to dual and once metric is present in everything, the imperial can be dropped.

    There is no reason for the Charlie P’s of the world to resist full metrication. If they don’t like metric only signs or labels, there is nothing stopping them from pulling out their calculator and converting it to any unit they want. Even to cubits if that makes them happy.

    Metric only road signs would be confusing to no one. As virtually 100 % of the UK population has had exposure to metric in one form or another over the last 50 years, All know it, even if they pretend not to. Even signs in metres they could view as yards if metres bother them. If a bridge sign says 4.3 m, and they view it as 4.3 yards, and if they truly have a feel for yards as they claim, 4.3 yards would be lower than 4.3 m and they would not attempt to go under the bridge if they thought their vehicle was over 4.3 yards. 4.3 yards is just over 3.9 m. The difference is 400 mm.

    Better this way than the the other where that 400 mm would mean a definite strike.


  11. @Jake
    Have you read the article? It is not about making roads safer, it is an opportunistic and gratuitous attempt to promote metrication above any road safety considerations.

    There is no reason to believe that two signs are better than one or that dual-unit signs are better than single-unit signs. And there’s certainly no evidence to suggest that UK lorry drivers are more in tune with metric measures than with imperial measures when it comes to avoiding low bridges.

    @Michael Glass
    That foreign lorries have a higher bridge strike rate than UK lorries is not an excuse to blame non-metric signage – because they have a higher rate for all types of accident – even those were units and signs are completely irrelevent. Some sources suggest that although only 1% of truck traffic is foreign trucks, that they account for 8% of accidents involving trucks. So you see they can have up to eight times as many bridge strikes as UK lorries before we need to start wondering what is making them more likely to hit bridges than to have any other sort of accident. Remember, correlation does not imply causation.

    My only motivation is to see fully considered and fully qualified analysis before jumping to conclusions. If most of the likely causes are ignored, then why would we take any conclusions seriously?

    As I said, its nothing more than opportunism to try to blame the signs when there are clearer and more obvious causes.


  12. Charlie P wrote: “There is a metric/imperial warning sign at the start of the road which the bus must have already passed before reaching the bridge, so the metric vs. imperial argument clearly has no validity in this case.”

    I have had a look at the Google Earth image of the street where the accident happened, as I suppose Charlie P did. There ‘is’ a sign on the street corner some 70 (!) metres before the bridge. Does that qualify as an acceptable place to erect the signage? The dual-unit sign is supposed to be on the structure itself. Since the bus would have been turning to enter the street it is highly probable that the driver did not notice the sign as he would have been manoeuvering the bus round the corner. The dual-unit sign is also mounted above a much larger ’20 mph zone’ sign which would probably catch your attention more than the hazard sign. There is a light above these signs which may or may not have been illuminated. After this there is a further imperial-only sign at the kerbside before the bridge and another imperial-only sign on the bridge. This is clearly not a good example of sign placement and the ‘metric v imperial’ argument, or rather the lack of a legal dual-unit sign on the bridge itself, is most certainly relevant, even if it turns out that it was not the direct cause of the driver failing to notice that his bus was too high for the bridge.


  13. Come on Haringey council roads department, Are you going to go metric or stay in the distant past, since the bridge strike what road signs have you displayed?
    Your views please.


  14. Hello CharlieP, I read your comment with interest. You questioned the need for dual signs because it had not been definitively proved that they are needed or that they would make a difference. It is possible that you are correct. However, the Department for Transport obviously felt differently, and that is why they made the dual signs mandatory.

    When I am forced to choose between the official opinion of the Department for Transport and your opinion, I would go for the official line unless I was presented with compelling evidence to the contrary. So far you have not come up with compelling evidence that would change my mind.

    It’s asking too much to expect foreign lorry drivers to read and understand heights and widths in a measuring system that is unfamiliar to them. They have to cope with driving on the left of the road, to signs in English, to speed limits in miles per hour and to distances in miles. On top of that, you expect them to be familiar with heights and widths in feet and inches when all they have known is metres!

    The Department for Transport has provided dual signs for heights and widths. It is quite literally the least they could do to help foreign lorry drivers. It is a wonder that they didn’t also consider providing dual distance and speed signs. Of course, the most sensible course would be to metricate all the road signs, just as Australia, New Zealand, Ireland, Canada and South Africa have done.

    In all, I think that you and your pro-Imperial mates should be very grateful that the Department for Transport has done so little and has taken so very long about doing it.


  15. @ Michael Glass:

    You said: “They have to cope with driving on the left of the road, to signs in English, to speed limits in miles per hour and to distances in miles. ”

    Actually, they don’t have to. They can completely ignore any mile signs and mile speeds. Most lorry drivers today have GPS and the GPS system will speak to you in the units and language you understand. The GPS will tell the driver in his native language any distance in metres and it multiples and give speeds in kilometres per hour.

    Maybe the GPS needs to be programmed to warn the driver that an approaching bridge is too low for his lorry to pass under.


  16. I think Daniel hits the nail on the head.

    A lot of drivers are reliant on GPS and when you’re outside your comfort zone you use whatever tools you can to get you from A to B. There was a recent news story about Sat Nav maps being updated to include bridge height details in an attempt to resolve this problem. It may help but whichever way you look at it people will still ignore signs thinking they know better rather than erring on the side of caution… some just aren’t concentrating and miss the signs.

    Personally I have my Sat Nav set to metric anyway; having passed my test 30+ years ago in the UK (and having learned nothing but metric in school) I just equate distances on road signs as minutes instead of miles and metres instead of yards and have no issues at all. That said I still break out in a sweat then I see a narrow width limit signed only in feet and inches. I can only imagine how a foreigner on our road feels when coming across something like this.

    I have also noted that, despite the change in the law, new restriction signs in roadworks are still imperial only. Doesn’t exactly fill me with hope!


  17. I’m glad the GPS system helps with distance and speed limit signs. However foreign drivers still have to drive on the left. Fortunately, the volume of traffic will usually take care of that issue


  18. The real problem, as I see it, is that there is no standard way in which a vehicle height is displayed to the driver. Is “4120 mm” really helpful, or should it show “4.2” m with the method of rounding being defined in law? One way would be to add 50 mm (or maybe 100 mm) to the real height and then to round upwards to the nearest 0.1 m. A similar rule already exists for Imperial units.


  19. If the driver of the private hire bus involved in the accident was not British, it is unlikely that this information will be made public. If the driver was an immigrant worker from the EU, that person would have benefitted from having the height of the bridge signed in metric units. At least it might have made the driver stop and think whether the bus would pass beneath the bridge. If he saw imperial units only, he might not even have recognised the sign as a height restriction. Even a dual unit sign would have been better than an imperial-only sign. If in actual fact the driver was British, then for a party bus it would probably have been a younger person who would have learnt metric at school. Again, every reason for a metric or dual sign. There is no way the lack of appropriate signage can be discounted as a factor in the accident. As the hire of buses for private functions during the evening and at night increases and the buses are driven on routes requested by the person hiring the vehicle, accidents such as this one are probably going to be a more common occurrence in the absence of proper signage or route planning.


  20. Could the accident on the Croydon tram be linked to driver confusion caused by the tram operating in km/h speeds and the road signs being in mph or a mixture of km/h and mph?


  21. @ Cliff says: 2016-10-29 at 00:49
    “Surely anyone can see that the safer option is to give a height restriction warning in units of measurement commonly taught in schools for over fifty years ( the official measurement system of the UK) rather than one given in an antique method of measurement only fully understood by people over fifty or sixty years of age.”

    It perplexes me as to why a factual post such as this should get 8 ‘thumbs down’. Quite clearly there are some out there who disagree that our roads should use the units of measure taught in our schools and which are the official government system of measure.
    Surely the pressure should be on changing the measures on the roads to reflect the education system and the official government line?
    13′-3″ would mean little to most drivers today unless there was an illuminated notice in the cab in EXACTLY the same format.
    Whether or not the sign is even part responsible is irrelevant, bus passengers in particular are at very high risk of death in these cases, and signage really should be taken more seriously.
    There is little point in persisting with units of measure that many do not understand.
    Education, not procrastination, should be the priority.


  22. @Cliff:

    Once again we see the perils of the metric muddle given your reasonable speculation about the possible confusion on the part of the tram driver.

    Added to that will be the posting of dual metric and Imperial height and width restriction signs (instead of just metric).

    The rub is that the UK can never go back to 100% (or nearly) Imperial. Since it cannot go backwards, it can only go forwards to full metrication if it is to ever escape the morass of the metric muddle.


  23. @Cliff:

    Possibly, though doubtful. The speed limit for that curve we are told was 12 mph, which no doubt is a conversion from 20 km/h. Even at 20 mph (32 km/h), the tram should have been able to negotiate that curve, given that there was no doubt at least a 50% safety margin. The worst that should have happened was that the tram simply derailed.

    For the tram to have actually overturned as it did, the speed would have to have been much higher. One report put it at 40 mph (64 km/h), and this would most certainly would be enough for the tram to overturn. I am surprised that it did not derail first, which would have probably kept the tram upright.

    But I do agree that having to constantly ‘change modes’ in terms of relating to speed limits is a recipe for confusion, if not today then one day, with a result similar to what we have seen in Croydon. Again (how many times!) time for the UK to go metric on its roads.


  24. @Cliff – since tram speed limit signs look completely different to those used for cars you would have to be a complete idiot to confuse the two. A properly trained tram driver should know the difference.

    I would also really hope that the speedometer in a tram would only indicate metric speeds making it highly unlikely that a driver would look at the wrong scale (does anybody have a definitive answer to this?)


  25. With regard to the Croydon incident. Croydon does indeed have metric tram speed limits and much of their network is separated from the roads. It is reasonable to assume that the drivers understand the the speed limit signs specific to trams (a black number on a white diamond with black outline) and that they indicate kilometres per hour. Also the tram speedometers will be calibrated in km/h. The curve where the tram turned over had a 20 km/h limit, dumbed down to 12 mph in most of the media reports. It is not unreasonable to assume that even if the driver had taken the corner at 20 mph (32 km/h), far less than what the media are claiming, then the tram may have remained upright.

    In any event, the Tyne and Wear Metro which began operation in August 1980 has always had metric limits, and all other tram and rapid transit systems opened since then have taken the same enlightened approach, and I know of no incident arising from confusion over units.

    If people had difficulty using different units then we would have to ban pilots and sailors from the roads, on account of not knowing whether to use knots, or miles per hour.

    Editor. A report today (2016-11-16) says that the tram was travelling at over three times the speed limit on the curve.


  26. Charlie P wrote last month: “So this appears to me to be yet another unfounded, opportunistic attack motivated by the desire to metricate at all costs (even if it means making the roads more dangerous) rather than the desire to make the roads safer.”

    It is hard to see how dual signs make the roads more dangerous than Imperial only when there is no guarantee all drivers know Imperial. The safest option would be metric only because it is international and almost certain that all British high vehicle drivers would know if a bridge was too low to pass under from an indication in metres.

    As for being opportunistic, it is quite normal for a campaigning organisation to use examples to illustrate their point when they can. We cannot prove it caused this accident but reasonable to suppose it may have contributed, given that it entailed a failure of judgement on the part of the driver.

    There is no logic to the patchiness of measurement units on signage in the UK. It is a mess and potentially dangerous. The cost of putting this right will be one off and longer term could be cheaper if we end up with metric only because they would be smaller, simpler and clearer than Imperial only or dual.


  27. The vast majority of the above comments rightly favour the uniformity of metric units everywhere in Britain, for the cogent reasons of safety, uniformity and simplicity. I cannot disagree with those motivations. But from my perspective here in Canada these laudable attitudes seem somehow at odds coming from a nation where weights (masses to be technical) are still often referred to in stones, horses are measured in hands, and beers are ordered in pints. Yes, old habits do die hard!

    We are in a worse muddle in Canada, where Metrication started by Trudeau 1.0 (Pierre Trudeau) in the 1970’s was stopped at about the 60% mark in the 1980’s. Ronald Reagan in the USA did not like Metrication, it seemed so un-American. The bitter-sweet story line with just a bit of humour thrown in, states that back then, President Reagan (known as the great communicator), whistled, making his buddy, the then Canadian Prime Minister Brian Mulroney, sit up, heel and cancel all further Metrication in our country. As a result, our Canadian supermarkets sell 454 gram Imperial pounds of butter, but switched to 500 g and 1 kg jars of peanut butter. “Oh, oh Canada!”

    It does not appear likely that Trudeau 2.0 (our present Prime Minister Justin Trudeau) will consider resumption of his father’s start of Metrication any time soon. Perhaps an imminent U.S. President would also frown upon any further Metrication, with Canada likely genuflecting agreement, and only a pragmatic hope of maintaining trade volume with the USA.


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