{"id":2292,"date":"2013-06-02T21:09:20","date_gmt":"2013-06-02T20:09:20","guid":{"rendered":"http:\/\/www.piglet-net.net\/pigblog\/?p=2292"},"modified":"2013-06-02T21:20:50","modified_gmt":"2013-06-02T20:20:50","slug":"motorway-madness","status":"publish","type":"post","link":"https:\/\/www.piglet-net.net\/pigblog\/?p=2292","title":{"rendered":"Motorway Madness"},"content":{"rendered":"

Back in December last year, Simon Guilfoyle, police inspector and systems thinker, published this rather good blog article: Life in the Fast lane<\/a>. He briefly explored what happens when the lane discipline goes wrong, and how capacity is reduced by that, but then moved on to use this as a parallel to managment and targets. He’s also done a similar thing with a visit to a pub<\/a>.<\/p>\n

Now, this stuff interests me, and I’d reccomend the blog to anyone, but I’d actually like to explore the motorway as a system, and what breaks it, and try to speculate why.
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\nSimon touches on this:<\/p>\n

\nAs you know, most motorways in the UK comprise three lanes. In police parlance, the nearside lane is called \u2018Lane 1\u2032; the middle lane, \u2018Lane 2\u2032; and the overtaking lane, \u2018Lane 3\u2032. (Note \u2013 Lane 3 is not the \u2018fast lane\u2019. Okay kids?)<\/p>\n

Anyway, the idea of this design is that Lanes 1 and 2 are supposed to carry the bulk of traffic, with Lane 3 coming into play for passing slower vehicles. When travelling along a motorway, if the lane to your left is empty, drivers should use it and not sit in the centre or outside lanes. To ignore this important rule of the road is selfish and disrupts the flow of traffic.\n<\/p><\/blockquote>\n

He’s right of course, and illustrates the problem with a sketch:<\/p>\n

\"Simon<\/a>
Simon Guilfoyle’s drawing of a congested motorway<\/figcaption><\/figure>\n

but at one point he suggests:<\/p>\n

\nindividuals place their own needs above those of the group \u2013 in this case, tending to gravitate towards Lane 3 in an attempt to get past everyone else, even though Lane 1 is relatively empty and the motorway would have been eminently capable of handling the volume of traffic if everyone \u2018cooperated\u2019.\n<\/p><\/blockquote>\n

Now, here we have a quandary. If we’re at the back of a block of traffic, at the car indicated by “me”, and we wish to go faster, we have 3 choices: we can sit there and wait, we can give up, and settle into L1 at a slower pace, or we could attempt to undertake.<\/p>\n

All have problems:<\/p>\n

Sitting there is taking part in reducing the overall throughput- adding to the queue- even though, if the road was clear in front, we’d overtake, and then move over, and L3 in this state typically suffers ripples of braking as cars from L2 push their way in, coupled with the inevitable slightly-too-close spacing that results.<\/p>\n

Giving up means we’ll be travelling slower than we’d like, though it will be more relaxing. <\/p>\n

Undertaking is not, as many people think, actually illegal. It is, however, a risky process, as people do not expect to be undertaken, and so may move without warning. It’s risky in another way, as it could be used as evidence of driving without due care and attention- so while it’s not an illegal move in itself, it could be considered as poor driving by a watching traffic officer.<\/p>\n

So, what do we do? The correct answer is that if only everyone followed the rules, the situation would not be as severe: throughput would increase, though there will still be a tipping point where the road is at capacity; this is what the variable speed limits on the M42 and M6 are intended to alleviate: if you lower speeds at very high densities, the ripple effect reduces, and you get smooth flow. At below this point, the “keep left unless overtaking” rule should mostly allow anyone to drive at their desired speed much of the time. The picture Simon drew shows a pretty typical moderately busy motorway, but it’s not uncommon<\/a> for a quiet motorway or dual carriageway to have the same problem, and I’d proffer the opinion that mostly, it’s those middlelanec*nts that are causing it: they’re leaving only one lane in which to pass them, and this causes the queue. Others may disagree<\/a>, with some people (including a few acquaintances) insisting that it’s “safer than all that darting in and out<\/a>”<\/p>\n

One further problem I’ve observed is that the L2 hoggers like to bunch together and tailgate- this can make getting back to L1 to leave the motorway hard- it can take the full length of the 1 mile marker at times.<\/p>\n

So, if I’m saying that incorrect lane use is a problem, why does it happen? It’s nothing new either, as this 1960s IAM video illustrates at 1:16 (though the whole video is worth a watch):
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