We all know the feeling. The end of a highway lane is looming ahead. You’ve been sitting politely in line for tedious minutes. All the while, cars zip past to merge only at the last second when their lane begins to fade away.
These drivers are the reason traffic trickles to a halt around construction and lane closures, right? Don’t they need to be stopped?
Wrong, according to the Virginia Department of Transportation.
These drivers, whether they know it or not, are using a tactic known as the “dynamic late merge,” where traffic fills all lanes and takes turns merging when the ending lane runs out. This is more commonly known as the zipper merge.
According to VDOT spokeswoman Brittany McBride Nichols, the zipper merge can make congested areas safer by encouraging predictable driving patterns and can even reduce the length of backups by up to 40 percent.
Nichols said the zipper merge can be helpful in any high-congestion areas where lanes are reduced. One example, the Interstate 64 widening project corridor, where lane closures occur nightly.
When all drivers are cooperating, the zipper merge achieves its goals by evenly distributing the traffic into the available lanes. This moves everybody at an even pace and shortens the backup length, restricting the congestion from affecting other areas of traffic. Not all drivers cooperate, but this might be because they don’t know how, says the Minnesota Department of Transportation, longtime advocates of the zipper merge.
The zipper merge is already common practice in many European countries, but in the United States it is still usually considered polite to merge as early as possible, according to VDOT.
“Some may also be hesitant to embrace the safer, more efficient zipper merge due to the anger some drivers experience towards other drivers getting a perceived advantage bypassing queued traffic when one lane is free,” Nichols said.
But this notion may be changing.
In 2017, VDOT implemented a zipper merge near a construction zone in Albemarle County over a 36-hour period. Spokesman Will Merritt said the zipper merge has been shown to help traffic flow smoothly, but it can only work if every driver knows to use that type of merge.
Though it has garnered growing support and use over the past decade, the zipper merge isn’t perfect. Many people assume its use would lower their commuting time, but according to a joint 2004 study from VDOT and the University of Virginia, this isn’t the case.
The study recommends the zipper merge in certain scenarios but insists on more field testing and investigation. It found that the zipper merge failed to reduce the length of drivers’ journeys by large amounts of time. A Minnesota Department of Transportation study found it didn’t cut travel time at all. Regardless, nearly all studies agree the zipper merge has the potential to make congested areas much safer.
In the meantime, there are plenty of the other tactics Virginia drivers can use to lower traffic congestion and positively impact the roadways, Nichols said.
She recommends keeping vehicles inspected and properly maintained, staying within the speed limit and driving distraction-free.
This story was published in partnership with our sister publication, WYDaily.
