The Wiki Man

Will self-driving cars know what to do in the middle lane?

The trick is that there's no one rule. Try doing that with an algorithm

15 February 2014

9:00 AM

15 February 2014

9:00 AM

I am convinced that when I took my driving test in 1983 I was asked by the examiner, ‘What lane of a three-lane motorway should you use when driving at a speed of 70 mph?’ And I am equally sure that the ‘correct’ answer to this question at that time, as given by the early 1980s version of the Highway Code, was ‘the middle one’.

My memory is that the three lanes of a motorway back then were designated 1) the slow lane, 2) the fast lane and 3) the overtaking lane. Whenever I mention this, however, no one else remembers anything of the kind. Rather predictably, about one in three people then takes the bait and embarks on a long rant about people ‘hogging the middle lane.’

In reality, this practice is much rarer now than it was a few years ago. As one motoring writer observed, middle-lane hogging is one of those problems — along with people leaving their rear fog lights on — which seem to have largely disappeared, but which are permanently retained on the list of things people like to rant about.


What is the rule? Some teutonically minded people say the rule is perfectly clear: you should always pull over to the left when there is space available to do so. Other people (wisely, I think) argue that it makes no sense to make traffic in the left-hand lane any denser than it needs to be, since that will slow everyone down.

I used to take the side of middle-lane ‘hoggers’. However, I now might answer the question in a rather perverse way. Which is to say that the only rule for using the middle lane is that there should be no rule; our instinctive ability to solve the problem may be superior to our ability to codify the solution. In fact, different ‘rules’ seem to apply depending on the level of traffic density and also on how many Audi drivers are on the road at the time (Audi is derived from the Latin verb audire, meaning ‘to drive annoyingly close to the car in front’).

What you have here is a very simple form of culture. A set of tacit rules which emerge to solve a social problem. There is a similar phenomenon among pedestrians: in some countries (including Britain) people instinctively turn to the right when approaching another pedestrian head on; in other parts of the world, people turn left. There is no formal rule: all that matters is that everyone does the same.

This entirely unconscious rule emerges through experience. According to Mehdi Moussaid of the Max Planck Institute in Berlin, if two approaching people guess each other’s intentions correctly, each moving to one side and allowing the other past, then they are likely to choose to move in the same direction the next time they need to avoid a collision. Eventually, and entirely without any conscious design, a local norm develops.

This explains why crowded multicultural places such as international airports can be fiendishly difficult to navigate, since all norms break down. To complicate things further, the distance at which people step to one side may vary from one culture to another. To many Europeans, Indian crowd behaviour may appear utterly bizarre and vice versa.

So, for the two decades or so in which driverless cars will have to share the roads with human drivers, safety and legality are not enough. Will they also be intelligent enough to adapt to local driving culture, which varies enormously across the world? Or will they drive perfectly safely and legally while annoying the hell out of the rest of us? It is the automotive equivalent of the Turing Test.

Rory Sutherland is vice-chairman of Ogilvy Group UK.

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  • mikewaller

    I think the underlying rule in respect of the middle lane ought to be that which underlies Christ’s “Do unto others” and Kant’s Golden Rule; put at its simplest, do nothing selfish. If, hand on heart, you genuinely believe that the inside lane is dangerously overcrowded, by all means use the middle lane. However if you use the middle lane simply because this makes life nice and easy for you and sod the rest, an eternity in Hell being roasted amidst endless repeats of Top Gear would seem to me a quite reasonable punishment.

    As for automated cars, I am put in mind of a science fiction story in which all mathematical skills had long ago been outsourced to computers with all warfare and transportation being carried out by driver-less vehicles. When, by chance, some inconsequential soul rediscovers mathematics, his is initially viewed as a dangerous charlatan. Then comes the blinding realisation that, instead of investing in all this increasingly expensive and still somewhat unreliable electronics, they could put humans in control at far lower cost. After all, they are eminently expendable, cheap and best of all, when something goes wrong, 100% of the blame can be attributed to them.

    • Tom M

      “….Then comes the blinding realisation that, instead of investing in all
      this increasingly expensive and still somewhat unreliable electronics,
      they could put humans in control at far lower cost…..”
      That reminds me of the office char lady. She was replaced by a coffee machine because she was too expensive.
      You can work out the similarity between that and the above comment yourself.

    • rorysutherland

      I agree. It probably works through mirror neurons – which I suppose make it possible for us to practice the Kantian imperative – as without a sense of empathy you can’t really follow it.

      Which suggests that the software needs to at least mimic empathy in some way.

      • mikewaller

        May I take this opportunity of publicly sharing with you a small factoid that is a kind of mirror image of your observation a few weeks ago that rather than just avoiding persecution themselves, a key objective of the puritans who went to New England was to be able to persecute those who disagreed with them.

        My matching piece relates to the other side of the country. Unsurprisingly, as the new white Australians started to make a go of things, they got more and more unhappy with the Motherland sending them large numbers of its social rejects and, in particular, the criminally insane. Reluctantly, Britain eventual agreed to stop the practice but, still wanting the benefits of the system, shifted to paying ships’ captains to somehow “lose” such prisoners elsewhere on the planet. Many of them settled for a then largely unknown land, what is now the Western Seaboard of the USA. What impact this may have had at the population level is, of course, very difficult to assess. But coupling this story with that of the persecuting puritans shows, I think, a commendable even-handedness with our American cousins! [:-)]

  • In2minds

    Will self-driving cars do that ‘winky-wanky’ thing with the indicators and
    follow really close like truck drivers? That’s a fun thing on a busy
    motorway.

  • Kitty MLB

    Self- driving cars will know what to do in the middle lane.
    Because being machines they would be programmed to do what
    is needed without the complexities, ego’s and issues of human nature.
    We, humans can just sit in the back reading and listening to music.
    By the way, I deplore motorways regardless of lanes.
    Once went round the M25 all day because I did not feel comfortable coming off
    the blasted thing, I am a competent driver by the way, but motorways,
    wretched things, like middle lane hoggers, and caravans.

  • saffrin

    The correct lane at 70mph is the inside lane. The other two are overtaking lanes, there is no such thing as a fast lane.

    • rorysutherland

      So everyone says. But I am convinced that a different rule applied when I took my test.

  • Perhaps they’ll just follow the law as you should.

    “You should always drive in the left-hand lane when the road ahead is clear. If you are overtaking a number of slower-moving vehicles, you should return to the left-hand lane as soon as you are safely past.”

    • rorysutherland

      It is not quite so simple. For one thing, if the left-hand lane becomes too dense, it becomes almost impossible for traffic to enter or leave at intersections.

  • Jackthesmilingblack

    Driving in the middle lane invites being “overtaken” on the left. Lane discipline is so poor on Japanese highways that I frequently make better progress plodding along the “slow” lane.
    Jack, long-term resident abroad

  • E Hart

    The speed limit is 70mph. If you are doing that you must either be in the middle lane on a not very busy motorway, or you’ll be weaving in and out of the overtaking lane likely an overly persistent fly irritating all those – and there are many – who are going much faster. Try driving at 70mph in the inside lane of any motorway and you’ll end up in the back of someone’s caravan or worse, you’ll have the “D” from Norbert Dantressangle impressed for eternity into your forehead.

    Supply has failed to rendezvous with demand. Space has brought us here, and we now have an ever-diminishing share of tarmac per car. It won’t matter who or what is driving the car – you won’t be going anywhere very fast. An average speed of 70mph or more – unless you’re driving between 2-4am – is already a dream.

    What happens when an algorithm runs into an old age pensioner heading the wrong way up the middle carriageway? Unlike us, it won’t have developed a side-step. Instead, it will duly point us straight onto the pensioner’s predicted trajectory whether foreign or not.

    There will be no feigning to go right, you’ll narrowly avoid Norbert Dantressangle on the left, and the car will careen between a caravan and an ice cream van into a family picnicking on the hard shoulder. Meanwhile, just before it melts, Tom-Tom will inform the algorithm that you’ve arrived at your destination. A pre-programmed message will then be sent from your “next-of-kin” app to outline to all concerned that you were carbonised at GMT… on so-and-so road… “I am so sorry… Have a nice day! Oh, and did, you know that you can get extra Nectar points on…”

    A government spokesman will announce that “lessons will be learned” but the findings will be inconclusive. After much ado, there will be a public inquiry at which a black box recorder will be played. All that will be heard will be Tom-Tom competing with Matt Monro’s “On Days Like These”.

    • Tom

      I’m not sure if you’ve driven in the UK much.
      If you are doing 70mph on most UK motorways, especially the M40, you will be in the slowest lane and having to find ways to speed up to 80mph to burst into the middle lane in order to overtake a “slow” moving lorry traveling a mere 65mph. While the outer lane cars speed by at 90-100mph.

      • E Hart

        Agreed. 70mph is a fictitious norm. As you suggest, you’d struggle to overtake all but the slowest at that speed.

      • Terry Field

        ”burst into the middle lane”
        Sounds like Mission Impossible!
        And on most British motorways, it is.

    • Tom M

      Love it.
      Try adding into the book of algorithm puzzles a group of youths with a tin of white paint painting white line circles for the algorithm to follow.

      • E Hart

        Yeah, that’s another of the variables. The casual hand and road-markings of fate. The car leaves the carriageway at the first service station. It skids on a discarded McDonalds Happy Meal and strips the petrol station forecourt of unleaded pumps before heading off at a tangent through the fence and over an area of Special Scientific Interest. In a hail of bee orchids, marsh buntings and natterjack toads, it finally comes to a standstill after colliding with a wind turbine and rolling down an embankment into a newly-dredged flood plain run-off feeder. On the radio, David Cameron is telling James Naughtie that nothing at all is no object. The army are called out to the rescue you. You phone your “loved ones” as the water rises, all the time chiding yourself for your selfishness, your lack of interest in Excel and for taking that stupid course on gin at Viceroy’s College. It will all be to no avail. The police arrive and strafe the car with bullets having got a tip-off from MI5 that you are Islamic fundamentalist from Boca Raton [sic]…

        At the inquest, the black box recorder will record Tom-Tom saying “turn left” repeatedly just as the Rev. Ian Paisley tells Kirsty Young that he’d like to take Celebrate Good Times by Kool and the Gang with him to the desert island.

  • Edward Noel

    I didn’t know Will Self drove cars.

    • Tom M

      Mmm if he does it will be badly and everybody else’s fault.

    • Terry Field

      Neat!
      Really good.
      Thank you!

      • Edward Noel

        Not sure whether you’re being genuine or sarcastic! Either way, sorry to be flippant.

  • rorysutherland

    I have a slight odd view in that I think that speed cameras are inappropriate on dual-carriageways: any multi-lane road becomes deeply uncomfortable if both/all lanes are travelling at the same speed: unlike Americans, Brits hate travelling side by side for longer than we have to. Hence if the left hand lane is going 50 when there is a temporary speed limit of 50mph, the lanes to the right are almost compelled to drive at 55mph and 60mph. So, unlike a conventional road, you don’t really have complete freedom of choice over your speed – it is to some extent dictated by the speed of the traffic around you. I suppose differential speed limits for the three lanes might work.

  • Terry Field

    Nobody knows what to do in the middle lane.
    It should be ploughed up and potatoes grown in it.
    Its function is as discernible as the Offside Rule.

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