The zipper merge

By Bill Taylor

It seems to me that nowadays I don’t get riled up much – doing so takes too much energy, raises the blood pressure, and gets the stomach acid into overdrive. Nope, for the most part I try to let things just slide like water off a duck’s back. There are a few occasions, however, when something gets my dander up – you know, a situation I can’t control and my options are both limited and ineffective.

Kinda makes a person want to use impolite language and gestures, hit something, and maybe pull at one’s hair (not a smart thing for those of us whose hair is rapidly disappearing). Understandable, but futile reactions. One of these instances occurs when I’m driving on a multi-lane highway – just cruising along when my comfortable little world is disrupted by a sign stating that one lane is closed ahead and drivers should merge into the lane remaining open as soon as possible. This common procedure is known as an “early merge.”

The ease with which drivers accomplish this maneuver depends largely on traffic density although composition of traffic such as the number of large trucks may also be a factor. If the highway is not crowded, that is, the vehicles in both lanes are spaced fairly far apart, drivers usually have little difficulty in moving to the lane remaining open. Large numbers of big rigs may make merging a bit more difficult, but generally, a bit of courtesy resolves that challenge. Yep, even with required speed reductions, traffic moves fairly rapidly. No big problem. Okay, so what is the problem?

It pops up when the traffic is fairly heavy in both lanes so vehicles are spaced as closely together as safety will permit. To merge two lanes into one means vehicles in the open lane must provide sufficient space for those in the closing lane to move over safely. The only way this can be done is for drivers in the open lane to slow down sufficiently to open space for the merge – which slows the entire open lane. Once again a bit of courtesy prevails. The result of this merging process is one lane comprising the vehicles from both lanes with the other lane being empty. Now here comes what gets my goat.

Almost always a few drivers whiz by in the now-empty lane, bypassing everyone who has dutifully merged. They then race to the location of the closure expecting to make their merge there. Who in tarnation do they think they are? Privileged characters or something? Whoa, Nelly! If those yahoos think I’m going to let them in, they have another think coming. Not on your tintype. Well, some high-falutin’ “traffic engineers” in some states are trying what they say will ease some problems associated with lane closures.

This procedure is known as “the late merge” – nicknamed the “zipper” merge. The way this works is drivers in merging lanes are expected to use both lanes to the lane reduction point and then merge by drivers in the both lanes alternately entering the choke point. This method gives rise to the nickname “zipper” because with drivers taking turns merging its kinda like the way the teeth of a zipper work. So what are the findings? Well, the “experts” say it “considerably reduces queue (“backup”) length (because drivers use the ending lane until its end). Jumpin’ Jehosaphat! It’s as plain as the nose on your face that loading both lanes with vehicles instead of just one would reduce the length of the backup. So what? Anything else?

According to one report, “The late merge method has not been found to increase throughput (throughput is the number of vehicles that pass through a point in a given period of time)”. How about them apples? The “zipper” merge doesn’t reduce the delay caused by lane closures. On the other hand, it may reduce the irritation, aggression, and “road rage’ brought on by drivers who race past in the lane that is closing and crowd back into line at the last second.

Yep, if everyone is in the same boat, the irritation factor goes down. I’m not sure how well the zipper procedure would work around here. For one thing it goes against everything we’ve practiced for years and it’s hard to teach an old dog new tricks. As far as I know our state still requires merging traffic to yield to through traffic and while most folks are considerate enough to assist merging drivers they are technically not legally wrong if they don’t.

Anyway, I don’t see any change in our lane-merge procedures for the foreseeable future which means those dadburned lane-jumpers trying to bulldoze their way in ahead of me can go whistle Dixie. It’s not much, but it may give me a bit of satisfaction and help reduce the stomach acid level. At least that’s how it seems to me.

By Bill Taylor

Bill Taylor may be contacted at

Bill Taylor may be contacted at