The zip merging debate: is it perfect sense or pushing in? We find out

Do you let people in when the next door lane is closed to traffic? (Picture iStock/oversnap)

The debate on how you merge into moving traffic when the lane you’re driving in closes is a fierce one. Do you stay in the closing lane to the very end, then merge in turn with the traffic in the open lane? Or do you move out of the closing lane as soon as you possibly can?

It’s a bit like whether you put cream on a scone before the jam or vice versa. Or perhaps even more fundamentally, whether you pronounce the word scone like ‘own’ or the other way. The law states that we should merge in turn, better known as zip merging. Yet only around a quarter of drivers (27 per cent) know this is the correct thing to do. Read on to find out why people who stay in the closing lane aren’t doing anything wrong.

What usually happens

You’re on a dual carriageway or motorway and you see signs warning that a lane is closing. Most of us – seven out of 10 according to a survey by Halfords – believe we should get into the lane that is staying open as quickly as we possibly can. This can result in hundreds of metres of perfectly usable carriageway lying empty. On top of that, 3 per cent of drivers actually think it’s OK to spread their car over two lanes to stop anyone else using the empty lane. That’s nearly three quarters of drivers (73 per cent) who’re wrong.

What the Highway Code says

Rule 134 of our road legislation states: “You should follow the signs and road markings and get into the lane as directed. In congested road conditions do not change lanes unnecessarily. Merging in turn is recommended but only if safe and appropriate when vehicles are travelling at a very low speed, e.g: when approaching road works or a road traffic incident. It is not recommended at high speed.”

What does that mean in practice?

If you’re in the lane that’s closing, stay there. Drive in it for as long as you can, then flick on your turn indicator and when it’s safe to do so, merge with the traffic in the open lane. Ideally, each driver in the open lane should let one driver from the closing lane in.

zip merging
Do you know what to do if you see one of these?

Why don’t we do this?

If the law states merging in turn is what we should do, why don’t we do it? Candace Gerlach from Green Flag believes it could be down to our nationality. “As Brits, queuing is in our culture,” she says.

“We like to queue and we’ve been brought up to think that being polite is the way forwards. That’s great but it doesn’t mean we should abandon the lane that’s closing immediately. And it doesn’t mean that anyone who’s making use of that lane is being rude. Britain is a small country with relatively crowded roads and we need to make use of as much of any open carriageways as possible. Merging in turn when it’s safe to do so enables us to do exactly that.”

What’s the science behind it?

Traffic engineer Ken Johnson from Minnesota in the US has conducted research into the pros and cons of zip merging. He discovered three main benefits:

  1. With two full lanes of traffic, the speed differential between lanes is reduced. With all traffic travelling at roughly the same speed, making the move from closing to open lanes is easier and safer.
  2. As all the available road is being used, the length of the queue is reduced by up to a half (40 per cent is common, according to Johnson.)
  3. With both lanes moving slowly and at similar speeds, everyone is disadvantaged. Drivers may not be happy that they’re in a jam but they can see everyone is in the same boat. The result? They don’t get as angry with other drivers, reducing the number of road rage incidents.

It’s not a perfect scenario but it’s making the best of a bad job and crucially, people moving in from the closing lane aren’t delaying people in the open lane or stealing any secret benefit. Ken Johnson explains: “Our analysis has shown that the zipper system has no effect on travel time. And it produces a much safer merge situation, making the length of the overall queue much shorter.”

There you have it: zip merging doesn’t penalise anyone. As Candace Gerlach claims: “We are saying: ‘come on guys, let’s start a movement’. We want to try to change people’s behaviour to embrace zip merging rather than frown upon it.”

36 comments on “The zip merging debate: is it perfect sense or pushing in? We find out

  1. Vernon 19/02/2019 8:20 AM

    Very sensible. It’s as it should be. Why so many drivers are so aggressive, racing around in a hurry getting nowhere, I will never understand. They should learn to ZIP IT.

  2. Eric Hayman 19/02/2019 9:38 AM

    Merge in turn is common sense. It is not “pushing in”. It is lazy drivers who cannot be bothered to pay full attention to driving who think of it as pushing in. Currently on the A338 coming off the A31 and towards Bournemouth, Lane One is in use only for Christchurch and the airport. Lane Two only for Bournemouth. The Bournemouth lane is much more heavily used, but long before the signs indicating which lane to use, Lane One is empty. So the occasional driver overtakes the Lane Two vehicles and then needs to get into Lane Two. Is that driver wrong? I would say no.

    • Momfer Undersand 25/02/2019 7:12 PM

      It is “pushing in” when the the driver wanting to join, Indicates one blink and whacks it in there assuming I’ll brake for him. And then goes absolutely nuclear because he wasn’t let in.
      Indicate and wait for the space, I’m more then patient enough to give space.

      • Eric Hayman 26/02/2019 4:12 PM

        On the road I have mentioned, the A338 – known as the Spur Road, where traffic joins the normally two lanes each way dual carriageway at the airport/Christchurch junction – you get the ‘push in” drivers, noticeably when going home in the afternoon, and too impatient to wait to be let in across the entry slip give way line. But this is not the merge in turn the original article was about; just one of countless junctions where traffic joins a major road.

      • Iain 21/09/2020 11:09 PM

        Exactly being pushed off the road by drivers that can’t be bothered even to indicate is a joke then those that ram the accelerator draw along side and force you to stop

  3. Ray Stevens 19/02/2019 9:19 PM

    anyone driving in the closed lane is potentially putting other vehicles drivers and passengers in danger, its closed for a reason, possible emergency vehicles may get stuck in trying to get to a hazard, by continuing on up the closed lane all they are doing is jumping to the front at best, worst of all flaming annoying to other road users, especially me….Europe when they close a lane everyone gets out of that lane early as possible end result is traffic moves more freely less potential for further dangers ensuing ….and if you are caught Not getting out of the closed lane potential for a heavy fine payment on the spot….. they should fine these drivers over here in the UK

    • Eric Hayman 20/02/2019 11:53 AM

      What closed lane? I was describing two open lanes, one eventually going to the left, one straight on. Only on nearing the divergence are there any signs to say which lane to take. It has nothing to do with blocking emergency vehicles. The only time I see UK drivers using closed lanes is on motorways, when the very clear red X is ignored. And on motorways when drivers are told by the matrix signs to merge, they are seen ignorantly using one lane only. By the way, the UK is part of Europe,

    • Martin Evans 08/04/2019 7:53 PM

      So is that your interpretation of the highway code? If so, you may want to look again. If everyone zip-merged near the point of closure it would be fine and keep the queue shorter and not blocking a nearby motorway exit.

      Martin – Advanced Instructor

      • Eric Hayman 09/04/2019 4:12 PM

        Martin – to whom were you replying?

    • keithmbreynolds 20/04/2019 3:10 PM

      you’re supposed to continue to the end of the lane then zip in… it’s very simple and safe.

      • Kaz 10/08/2020 4:24 PM

        no it is not safe. if your lane is closing you should change lane when it is safe to do so not in the last couple of meters of it. you have to watch front and back of your car at the same time to merge in and adding obstacle in front of you forces you to react even if it is not safe to do so.

  4. Eric Hayman 21/02/2019 3:10 PM

    Thank you, John. I was simply giving an example of where lane changing is required because of what the local council is doing in connection with a new road scheme. Because Lane Two is much more heavily used than Lane One, it is inevitable that most of the movement will be into Lane Two. And not until the first warning sign is there any indication that each of the two lanes of the southbound carriageway will lead to a different destination.. “Merge in turn” is an official sign, used countrywide. What is the problem? Do non-mergers also disobey other road signs? Merging makes the best use of road space, and reduces long tailbacks. All it requires is politeness from the Great British Public.

  5. Phil 08/04/2019 7:29 PM

    The problem with merging too early is that many inconsiderate drivers see this as an opportunity to speed past and seek to jump the queue. This annoys other drivers who then straddle both lanes to stop them. In my opinion the signs should say when to move over. i.e the point at which you should start to merge and the point at which you must have done so.

    • Mark Thompson 05/03/2022 10:36 PM

      In slow moving traffic, the point at which to merge is at the front, where the lane closes. People merging too early are merging… too early.

      Hope that helps.

  6. Norman ELLIOTT 08/04/2019 7:41 PM

    If people in the lane which remains open slow down and leave enough room for one car in the closing lane to merge in then there should be no problem. Apart from a genuine emergency I see no reason why so many race everywhere. Why can’t people just be considerate? However when I am joining a motorway I do find that almost all drivers sensibly allow me to merge in and I do when I see someone joining the flow so why not when it’s an imminent lane closure?

  7. trevorjmallett 08/04/2019 9:11 PM

    This so called zip in is a waste of time all it does is slow the traffic and cause more delays so that people can push in at the front because they feel that deserve to be in the front.

    • Eric Hayman 09/04/2019 4:14 PM

      trevorjmallett – then what is your plan for when lanes merge? Please tell us.

    • Martin Evans 09/04/2019 4:28 PM

      It’s the official recommended method and if done correctly, doesnt slow the traffic any more than changing lanes early. It has the advantage of keeping the queue shorter thus not blocking an earlier motorway exit – allowing others to leave the motorway unhindered.

    • CP 04/09/2019 5:29 PM

      Done properly no-one can push in at the front. The point is for the traffic to be split evenly across both lanes and merge in turn, so both lanes move at the same speed and all the road is used safely. It’s everyone moving into one lane way ahead of the merge point that creates the unequal situation and the danger.

  8. Kevan 09/04/2019 7:16 AM

    I generally move iout of the lane that is closing in good time and safely. I would then let another car change lanes in front of me. This doesn’t slow me down appreciably, is good road manners and seems the sennsible thing to do. Those selfish drivers who leave it late cause the flowing lane to slow down to let then in. Zip merging is obviously the best way.

  9. Evert Frijlink 09/04/2019 8:06 AM

    Rather interesting this debate.. Weird to think that, when I did my driving licence in 1977 in Germany, I was taught to do just this.. merge in turn..

  10. Steve dunford 09/04/2019 8:23 AM

    Zip merging will only work if there is space to merge into ( As in a Zip ) when drivers keep proper distances. It won’t work where drivers think the stopping distance at 60 mph is 6 feet.

  11. Richard Shaw 09/04/2019 12:25 PM

    merging too early does not meet the highway code ‘zip in’ guidelines, and in fact causes delays for drivers already in the open lane, as more cars merge ahead of their turn. staying in lane and merging at the end ensures you merge one for one which is fairer.

    • Norman ELLIOTT 09/04/2019 8:55 PM

      Well it would do if those on the closing lane didn’t get so near the end that to let them in the person in the open lane has to slow right down even to the point of getting into first gear otherwise they would run into the back of the one merging and we all know they would be found guilty of driving too close to the one in front.

  12. Eric Hayman 09/04/2019 3:26 PM

    Phil – Have you not seen MERGE NOW signs? On 6 Apr 2019 I drove up the M3 and took the M25 towards Heathrow. A car had broken down about half a mile before the start of the slip road, and matrix signs above Lane 1 of the two lane slip had Move Over white arrows for over a mile, followed by the Red Cross – Lane Closed – sign.

    All four lanes – those for the M25 and for the continuation of the M3 towards London – were at a standstill for over a mile. Why the outer two lanes were not moving did not make sense.

    Drivers were moving from the Lane 1 to the Lane 2 of the slip with no problem, I saw no vehicles ignoring the Red Cross; no doubt because there would have been an ANPR camera on the gantry.

    BUT – just where the hard shoulder began on the slip – this part of the M3 is now a STUPID motorway – there was the “Stranded Vehicle”, a car, with a Traffic Land Rover next to it. So – why the Red Cross still closing Lane 1? Why the Move Over arrows still showing? Just another example of refusing to get traffic moving after an accident as soon as practical.

  13. Michael Blissett 09/04/2019 9:41 PM

    As an IAM advanced driver I agree we should always use both lanes and ZIP merge in turn using manners and not getting aggravated. I have seen some councils now putting up signs saying merge in turn and I think more councils need to do this so drivers are aware of the rules of the highway code.

  14. Jeff 10/04/2019 6:59 AM

    The drivers who cut in as close as possible to the end of the ‘closing lane’ have no appreciation of this science, they are simply looking to jump the queue and it’s because of this that other motorists get annoyed.

  15. Barry 11/04/2019 7:09 AM

    Zip merging, the Dutch seem to do without agro why do we get so uptight. It makes much more sense , is safer and every one is equally disadvantaged.

  16. Sue 11/04/2019 7:36 AM

    Merging in Turn is logical and does work but very rarely do you see signs up to advise drivers. This is all people need. Contractors need to put these up alongside the lane closure signs. Then there will be less bad feeling & delays.

  17. Nigel Taylor 11/04/2019 10:33 AM

    It’s all so obvious! Zip-up is always correct, There is NO priority just because a car is in lane X. Those in a closed lane (or a merging acceleration lane for that matter) have as much right as any other…just zip-up and behave as a co-operating adult. On motorways, this concept reduces the ridiculous scene in which there’s, say a mile of queued traffic and empty lane(s) alongside.
    ….also, I say, there is no need to indicate change lanes because zip-up is the RIGHT of those in a blocked lane. What do others expect ….that blocked drivers drive into a hole, or just die of hunger whilst waiting for “permission” ? Ridiculous !
    The more interesting debate is that those in a give-way urban side road, when jambed-up, have as much right to proceed as those on the “main” road, and again all should zip-up and not have to suffer self-righteous indignation from those on the “main” road who insist on their apparent “right”.
    The purpose of give-way priority is to avoid accidents. This applies only when traffic is moving. When jambed, there is no purpose to this rule.
    Adult co-operation rather than indignant unthinking (useless) rule enforcement is the key to progress.

    • Anthony 16/10/2019 7:42 AM

      Please don’t suggest that there is no need to signal before changing lanes. There are enough people with bad habits already. However I can see your point if the system is working properly and everybody is merging at the same point.

  18. Berni 11/04/2019 11:45 AM

    I say,zip in turn at an appropriate speed into a space as you would do on a Slip On road to a motorway (as many donn’t ).

  19. N Young 12/04/2019 12:23 PM

    I feel that we should follow the rule of the Highway Code, the problem when you have a situation where there is a lane closure in place most of the drivers on the road are not considerate enough to allow a car to filter into the other lane they are so selfish and inconsiderate and they have a notion of I cannot let anybody get ahead of me.

  20. Brian 22/04/2019 10:32 AM

    Common sense should dictate that traffic flowing at the same rate in all lanes would allow the ZIP principle to work. But if as usual the traffic in the open lanes is flowing slower than the clear lanes, someone flying down the blocked lane and at the last second veering in at the front could cause an accident knock on effect with. Many drivers would simply use this as a means to jump the queue. Think of it as supermarket queues, would the ZIP idea work, of course not and the same on the road. I reckon the principle is seriously flawed by human nature,

  21. Michael 30/06/2019 9:26 PM

    I can see the advantage of zip merging at the end, but it only really works if everyone or at least most people agree and play the game. When 90% of people obviously prefer to get in lane early and you are one of the 10% who insist on leaving it til the last moment, don’t be surprised if you are regarded as a queue jumper because that is what you are. Also, despite what the HC says, you have no right to expect people in the other lane to co-operate. You are changing lane and it is entirely up to you to ensure it is safe to do so before you move over. It is not custom and practice in the UK and one is not driving with consideration if you insist it is.

  22. Holly Merry 15/12/2019 1:44 PM

    If they seriously want to change driver attitudes and behaviour to encourage this zip-in merge in turn method, then they need to do a huge sustained advertising campaign to that effect nationwide. TV ads, billboards, bus stop and back of bus signage. I still remember the “clunk click every trip” ads that were used when the law on seat belts was introduced, also the “only a fool breaks the 2 second rule” campaign to encourage safe gaps between traffic on motorways. A new road safety campaign is now required to address the zip-in/merge in turn scenario.

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