Police and the Highway Code have confirmed that the correct way to merge when two lanes become one is to use both lanes until the merge point and then take turns, a technique known as zip-merging. Drivers who deliberately block others from using the open lane risk prosecution for careless driving, which carries a fixed penalty of £100 and three points on a licence.
The situation arises most often at a permanent lane reduction or during roadworks, such as on a motorway where one lane is closed. Many motorists are unsure of the proper approach, and one Cardiff driver said: "I'm not sure anyone knows for certain what the rule is. But judging from how frequently you get drivers in the left hand lane doing their best to stop you merging in from the right, I'd imagine most people think those wily right hand lane drivers are just trying to stitch them up and jump the queue."
What is zip-merging?
Zip-merging means drivers should not move into a single lane immediately upon seeing a lane closure sign. Instead, they should continue in both lanes and merge alternately, one vehicle at a time, at the actual point where the lane ends. The name comes from the way the manoeuvre mirrors the interlocking teeth of a zipper, and it is believed to substantially reduce traffic jams.
Police forces, the Highway Code, the RAC and National Highways all agree on this approach. Avon and Somerset Police explained that the technique "helps make full use of the available road space" and noted: "Problems tend to arise when drivers are unwilling to allow others to safely merge, or when motorists change lanes aggressively, without adequate observation, signalling or consideration for other road users."
Highway Code rule 134
Highway Code rule 134 covers lane-merging, stating: "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."
National Highways echoed this guidance, stating: "By keeping both lanes in use until the merge point, congestion is minimised and journey reliability is improved."
Why merging early creates longer queues
The RAC concurred, stating: "When motorists encounter a lane closure on a motorway or dual carriageway, the majority of drivers follow the etiquette of moving over early, but this creates one long, slow line of traffic and a near-empty outside lane."
"While motorists on the inside lane might think they're doing the right thing, it can be more beneficial to continue using the open lane until the last minute, utilising all of the available road and then 'merging in turn' at the point at which the road narrows to a single lane."
Although many drivers find it annoying to watch others use the outside lane while they sit stationary on the inside, two lanes of slow-moving traffic are better than one. If cars use all of the space available on both lanes, the line of congestion should disappear or at least reduce.
Fine for incorrectly merging lanes
Drivers will not face a fine for queuing in the left lane too early, nor for using the empty lane right up to the merger point. However, attempting to block someone from using the emptier lane could lead to prosecution for careless driving, or potentially something more serious. The fixed penalty for careless driving is currently £100 with three points on the licence.
National Highways said: "Dangerous, careless or inconsiderate driving can occur if a driver forces their way into traffic, deliberately obstructs other vehicles, or carries out manoeuvres which create a risk of collision."
If a driver is blocked by someone who does not understand the correct way to merge, the advice is to keep calm and not react with anger. Dashcam footage of suspected driving offences can be submitted to Operation Snap, a UK police initiative that allows the public to upload video evidence.
