Tag Archives: m4 bus lane

The M4 bus lane (repeat)

I heard Radio 4 news report that the Games Lane™ on the M4 in west London came into force today and that there had been “no noticeable effect on the rest of the traffic”. Of course there was no effect on traffic: the Games Lane™ is just the old M4 bus lane, de-restricted in 2010 by the then new government. The bus lane was just an engineering hack, and abolishing it was always a pointless political gesture that could do nothing to help the Motorist. This seemed like a good excuse to re-publish this 2 year old post on why.

I rather let the announcement of the removal of the M4 bus lane pass without comment during the busy period, but with work commencing on painting over the lines, it seems a good moment to revisit the topic. Because while the M4 bus lane was never a remotely important feature of the national or local transport system, and the effect of its removal will be negligible, it has always been of huge symbolic significance.

The short stretch of bus lane at the inner-London end of the motorway was introduced in June 1999 by John Prescott — one of our best and most progressive transport secretaries (one of those non-achievements like “best British cycle route” or “most likeable cab driver”) — and was something new and difficult to understand. The government tried to explain how it would help everybody, how Motorists themselves would benefit from it, but all anybody heard was that the amount of concrete that Motorists could put their cars on was going to be reduced for the first time ever. The media were desperate for it to fail. What if it set a precedent? Take this fabulous rant from a BBC correspondent, in the days before BBC correspondents had their teeth filed for fear that they might be accused of anti-Tory bias.

The M4 bus lane was the symbol of the first government that had ever shown signs of recognising that the country has a dangerous car addition; the first ever road policy whose entire purpose was not to make it easier for more people to drive more cars further and faster. And in the tabloid media fantasy world, that amounted to a declaration of war on the motorist.

The irony is that the purpose of the M4 bus lane was not any different to any roads policy that had come before. It was introduced to smooth the traffic flow: to make journeys faster, easier and more reliable for motorists on the M4. The issue is explained with nice diagrams here. I won’t try to explain the whole thing in words (well, I did try, and failed, and deleted it), but the take home message is that the rate-limiting step for this section of the M4 is a bottleneck at Brentford that can never be eliminated. Where that bottleneck occurs, three lanes became two, causing merging and lane-changing throughout the three-lane section — behaviours which are known to slow overall traffic flow. By effectively making the M4 consistently two lanes wide, the bus lane is in fact a clever hack to make the traffic run more smoothly and reliably. It needn’t be a bus lane at all, it only needs for this section to be consistently two lanes wide instead of three lanes merging into two.

And it works. Despite having less space, and despite the reduction in speed-limit that coincided with the change in layout, journey times for all road users fell after the bus lane was introduced. (Only by seconds — it’s a very short stretch of road — but you know how much a second means to a Motorist.) And with less lane-changing, accident rates fell. Even the Daily Mail had to acknowledge that it had been a successful implementation of an evidence-based intervention for improving journey times, reliability, and safety.

But this was soon forgotten, because it just didn’t feel right. An empty lane that you’re not allowed to use doesn’t feel like it’s helping you when you’re stuck in a traffic jam, especially given the absurd rule that allowed rich businessmen to sail past in their taxis from the airport to the city (and still allows them to do this in most remaining London bus lanes). And the fact that it was a bus lane, not a hatched-out or fenced-off wasteland, seemed to make an important difference to many people — the AA took the bizarre stance that the lane’s success could only be measured in modal shift; that any other beneficial effect would be a failure. By the time Philip Hammond decreed that in the name of ending the War On The Motorist the lane must go and the road revert to three lanes, no journalist could remember it being anything other than Prescott’s folly, a joke on a road that is barely used by buses, and the cause of much Motorist misery. No journalist mentioned that it had once been hailed as a great success independent of its role as a bus lane. No journalist questioned the received wisdom that the bus lane was a stupid, pointless, unfair, in-your-face ideologically anti-Motorist waste of money.

The lane improved journey times by seconds. Removing it will probably worsen journey times by seconds. It will affect cabbies marginally more, and every few days the Motorists will close the road by smashing up their cars when changing lanes. It doesn’t matter; it never mattered. But installing it had the symbolic significance of suggesting that the government might, for once, now and then, just consider transport policies that go beyond Motorism; to occasionally provide for more than just the car user. Its removal is the symbol of the opposite stance: that this government will continue to provide for the car, and nobody else.

But more than that. By removing the M4 bus lane, Philip Hammond is telling us that this government will happily pursue policies that hit the Motorist, so long as they hit the non-Motorist harder. This is the deliberately spiteful act of a government that cares for dogma not evidence.

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Queuing

I’ve been meaning to write a bit more about the M4 bus lane, but haven’t had the time, so here’s a rather crude brain dump while I sit in the dark on a bus somewhere on the A9 in the snowy Cairngorms.

The Dutch infrastructure minister recently announced that speed limits on some stretches of motorway would be raised.  This would not help Motorists get to their destinations any quicker, she noted, but it was a change worth making because it would make the motorists feel better.  Aside from being a delightfully refreshing piece of honesty from a politician, it highlights again that behaviour and psychology should not be ignored when designing transport policy.  Philip Hammond should have been this honest when abolishing the M4 bus lane — instead of the weak nonsense about improving journey times, just tell the truth that it’s a cheap way of making Motorists feel better.

The M4 bus lane was designed to cut the journey times of Motorists entering London — to make their journeys faster and more reliable, and thus to cut the <insert absurd made up number here> billions of pounds that the Institute of Directors like to claim is lost because of their Jags being caught in congestion their supply chain being delayed by congestion.  The Motorist probably thinks that he too would like his journeys to be faster and more reliable.  But this is not quite true.  The Motorist would like his journeys to seem faster and more reliable.

The M4 bus lane was hated not because it increased car journey times or made journeys less reliable.  It didn’t.  As previously explained, the bus lane was a clever hack to the layout of a road with a bottleneck.  It made a tiny and irrelevant cut to journey times, while cutting lane changing and accident rates and thus greatly improving consistency in journey times.  The bus lane was hated because motorists thought it increased their journey times.

Part of it was the problem of common sense.  The likes of Jeremy Clarkson and Terry Wogan despise those scientists and academics with all their fancy facts and data — the problem with these researchers is that they don’t have any common sense, and common sense tells Clarkson and Wogan that taking away one lane of the M4 must have caused traffic jams.  No amount of your facts can change that.

Another part of it was recall bias: all of those massive pre-bus lane jams begin to blur into the distance, whereas this jam that I’m sat in right now is real — and hey look, there’s a bus lane.  Coincidence?

But it was more than this.  It was about people’s perception, and particularly people’s perception of queues.  Since I’m on a bus with no reference material and limited battery life, I’ll put it in bullet points:

When sat on a Motorway in a traffic jam, Motorists usually believe that their own lane is going the slowest.  It’s simple: when their own lane is moving freely, they’re concentrating on driving, and don’t notice that the other lanes are stationary; when their lane is stationary, they have nothing better to do than stare at all the vehicles which are moving freely in the other lanes.  So even if over time all lanes even out, the Motorist perceives that the other lanes are moving better — especially if the jam is severe enough that they spend more time stationary (observing others moving) than moving themselves.   (Hence all the futile changing of lanes in jams, which just makes the jams worse.)  This is the same reason why in the Post Office — wait, do blog readers even still use those?  OK, this is the same reason why in the ticket office at a major station, you have a single queue serving several windows, rather than independent queues.  Independent queues make people nervous about their decisions.

This perception leads to Motorists overestimating their time sat in traffic, and it’s made worse when they can see moving traffic — if the opposite carriageway is moving freely, or there’s a parallel un-jammed road, then the sight of moving cars merely serves to remind the poor stationary Motorist of their own lack of motion.  Drivers asked to estimate how long they were stuck in traffic consistently over-estimate the jam if they see other traffic moving freely.

So the M4 bus lane was about the worst thing you could do if you wanted Motorists to perceive that they were spending less time in queues.  Now when they were sat in a queue they weren’t just sat there with nothing better to do than get paranoid over the relative speed of the two lanes of traffic: they could also sit there watching the buses and taxis and prime-ministers go past at speed, constantly highlighting the fact that the Motorist was going nowhere.

The research shows this — have drivers estimate their queuing time with and without visible moving traffic nearby; or compare the driver and passenger experience of a stop-start motorway jam. It’s just another of the many fascinating little quirks of psychology — one of the bizarre things our brains do when confronted with absurd man-made situations like traffic jams.  You can make Motorists happily spend more time sat in traffic jams, simply by making them sincerely believe that it is less time.

(Somewhen I’ll try to find some interesting references, but 3G has just dropped out…)

The M4 bus lane

I rather let the announcement of the removal of the M4 bus lane pass without comment during the busy period, but with work commencing on painting over the lines, it seems a good moment to revisit the topic.  Because while the M4 bus lane was never a remotely important feature of the national or local transport system, and the effect of its removal will be negligible, it has always been of huge symbolic significance.

The short stretch of bus lane at the inner-London end of the motorway was introduced in June 1999 by John Prescott — probably our best and most progressive transport secretary ever (which is one of those non-achievements like “most reliable train operator” or “most likable cab driver”) — and was something new and difficult to understand.  The government tried to explain how it would help everybody, how Motorists themselves would benefit from it, but all anybody heard was that the amount of concrete that Motorists could put their cars on was going to be reduced for the first time ever.  The media were desperate for it to fail.  What if it set a precedent?  Take this fabulous rant from a BBC correspondent, in the days before BBC correspondents had their teeth filed for fear that they might be accused of anti-Tory bias.

The M4 bus lane was the symbol of the first government that had ever shown signs of recognising that the country has a dangerous car addition; the first ever road policy whose entire purpose was not to make it easier for more people to drive more cars further and faster.  And in the tabloid media fantasy world, that amounted to a declaration of war on the motorist.

The irony is that the purpose of the M4 bus lane was not any different to any roads policy that had come before.  In today’s favoured terminology, it was introduced to smooth the traffic flow: to make journeys faster and easier for the Motorist on the M4.  The issue is explained with nice diagrams here.  I won’t try to explain the whole thing in words (well, I did try, and failed, and deleted it), but the take home message is that the rate-limiting step for this section of the M4 is a bottleneck at Brentford that can never be eliminated.  Where that bottleneck occurs, three lanes became two, causing merging and lane-changing throughout the three-lane section — behaviours which are known to slow overall traffic flow.  By effectively making the M4 consistently two lanes wide, the bus lane is in fact a clever hack to make the traffic run more smoothly and reliably.  It needn’t be a bus lane at all, it only needs for this section to be consistently two lanes wide instead of three lanes merging into two.

And it works.  Despite having less space, and despite the reduction in speed-limit that coincided with the change in layout, journey times for all road users fell after the bus lane was introduced.  (Only by seconds or minutes — it’s a very short stretch of road — but you know how much a second means to a Motorist.)  And with less lane-changing, accident rates fell.  Even the Daily Mail had to acknowledge that it had been a successful implementation of an evidence-based intervention for improving journey times, reliability, and safety.

But this was soon forgotten, because it just didn’t feel right.  An empty lane that you’re not allowed to use doesn’t feel like it’s helping you when you’re stuck in a traffic jam, especially given the absurd rule that allowed rich businessmen to sail past in their taxis from the airport to the city (and still allows them to do this in most remaining London bus lanes).  And the fact that it was a bus lane, not a hatched-out or fenced-off wasteland, seemed to make an important difference to many people — the AA took the bizarre stance that the lane’s success could only be measured in modal shift; that any other beneficial effect would be a failure.  By the time Philip Hammond decreed that in the name of ending the War On The Motorist the lane must go and the road revert to three lanes, no journalist could remember it being anything other than Prescott’s folly, a joke on a road that is barely used by buses, and the cause of much Motorist misery.  No journalist mentioned that it had once been hailed as a great success independent of its role as a bus lane.  No journalist questioned the received wisdom that the bus lane was a stupid, pointless, unfair, in-your-face ideologically anti-Motorist waste of money.

The lane improved journey times by about one minute.  Removing it will probably cut journey times by about one minute.  It will affect cabbies marginally more, and every few days the Motorists will close the road by smashing up their cars when changing lanes.  It doesn’t matter; it never mattered.  But installing it had the symbolic significance of suggesting that the government might, for once, now and then, just consider transport policies that go beyond Motorism; to occasionally provide for more than just the car user.  Its removal is the symbol of the opposite stance: that this government will continue to provide for the car, and nobody else.

But more than that.  By removing the M4 bus lane, Philip Hammond is telling us that this government will happily pursue policies that hit the Motorist, so long as they hit the non-Motorist harder.  This is the deliberately spiteful act of a government that cares for dogma not evidence.