The most efficient way for a line to move is to cut
It’s rare for frustrations to build on the highway at a standstill and have anything to do with the mechanics of the problem. When a driver passes single-file traffic to zip down an otherwise unused lane leading up to a merge, deep emotional reactions kick in-all thanks to the etiquette classes we learned in grade school. From the child who was meticulously taught that taking turns is the highest form of civic duty comes the motorist whose rage at “cutting” appears less like an annoyance and more like a sign of blatant societal collapse. It is at this point, miles from the actual lane drop, that well-intentioned drivers voluntarily narrow their lane, inadvertently preparing for massive gridlock.
The mathematics have long been settled for traffic engineers. Properly utilizing both available lanes to the absolute last bit of pavement available to them (known as a “zipper merge” by a variety of state DOTs around the world) gets the maximum number of vehicles through. Cars effectively alternate going into a merging point the same way that teeth interlock.
This strategy uses available space instead of creating waste, shortening traffic backups by as much as 40% and allowing congestion to drain before overflowing into road intersections, highway ramps and emergency routes.
Furthermore, smooth, controlled movement toward a single destination reduces traffic cascading over the roads and eliminates the dreaded “stop and go” phenomenon.
Those who claim that driving all the way up an open lane is “cutting” are operating on the outdated assumption that what works at a grocery store or ticket counter will work at 70 miles per hour on a highway. In such static settings, one’s move ahead of the pack is directly at the expense of others but adds nothing to the overall efficiency of the situation. By not utilizing an empty lane of a highway, “polite” drivers are doing more than just being patient; they are wasting the infrastructure that others have paid for with taxes while causing traffic to build. Late merging is not theft of line position; it is intelligent filling of available space that would otherwise contribute to a lengthy traffic jam.
Simply informing road users what math tells us to do cannot fully overcome deeply ingrained instinctual bias-and this must change. State Departments of Transportation around the world have begun using highway messages that instruct drivers to “USE BOTH LANES TO THE MERGE POINT.” Dynamic message signs, in particular, serve to legitimize the late merge and help drivers understand that rather than being a rude “cutter,” they are doing what traffic engineers say they should. Once the police and highway agency encourage the “zipper merge,” social anxiety melts away and a more cooperative road culture emerges where it becomes to our collective best interest to maximize capacity instead of getting angry.
