READING, Pa. — We’ve all been there.

Bumper to bumper and going nowhere in a single-file line of vehicles as two lanes of traffic perform the seemingly impossible dance of becoming one.

You stare ahead, trying to see what’s causing the highway backup that’s sure to make you late for dinner. Construction? An accident?

Then, without fail, it happens.

A car zooms past in the empty lane and then tries to merge ahead of you like, it seems, a kid jumping in the lunch line. You’re glad to see that other motorists, those who waited their turn like you, refuse to let the son of a gun in.

But what most traffic experts say about merging will sting. The person who drove up the empty lane was merging properly. And that backup you’re sitting in? It was caused by drivers like you who merged too early.

The late merge — also known as the zipper merge — has proved to be the safest and most-efficient way of merging highway traffic into one lane, experts say.

But, they warn, many drivers don’t think it’s an acceptable strategy, mostly because it clashes with everything we’re conditioned to think of as appropriate.

Laws in most states, including Pennsylvania, offer little guidance.

The result is a free-for-all on the highway and the tendency for arguments to turn bitter at the very mention of the word “merge.”

BEST PRACTICE, IN THEORY

In a late merge, both lanes are used until the merge point. Then vehicles from each lane take turns going forward. Typically, signs tell drivers to stay in their lanes and when to merge.

A University of Nebraska study that’s often cited by late-merge advocates found that the method allowed 15 percent more traffic to move forward than early merging. It also found that in heavier traffic, forced merges dropped by 75 percent and cases of drivers straddling both lanes fell by 30 percent.

The idea is that the traffic is spread over multiple lanes and there’s only one merge point, rather than drivers trying to move over at different spots, which slows traffic.

“If there’s capacity there in both lanes for traffic, both lanes should be used for traffic,” said Michael Golembiewski, a Berks County transportation planner.

But working in theory and working in practice are two different things.

“It’s known that as long as people let people in, you can maintain traffic flow,” Golembiewski said. “Unfortunately, it takes that common courtesy that many drivers don’t display.”

FALLING IN LINE

There’s one big reason that traffic backs up into one lane at highway work, according to Dr. Leon James, a University of Hawaii psychology professor and nationally recognized expert in traffic and driving behavior.

Most Americans believe early merging is the correct strategy and are passionate in thinking they’re right.

States just began experimenting with late merges within the last 15 years. Even younger drivers are conditioned to merge early because they grew up watching their parents do it.

Fear also plays a role.

“A lot of people merge early because of the idea they have that if I get all the way to the end - late merging - then people won’t let me in and I’ll be stuck there,” James said.

That’s irrational, he said. Maybe one or two cars will block entrance to the continuing lane, but someone will leave room.

But there’s another side to that fear, he said. Drivers know that if a long backup of early mergers is starting to form, bucking the trend would be viewed as line-jumping and just plain inconsiderate.

And few offenses hit quite the same nerve with people as rudeness. Not wanting to zip past a long line of angry stares or nasty gestures, most drivers just take their place at the back of the line, making the traffic worse.

A lot of that mistrust could be eliminated if people stopped looking at each other as malicious or rude, James said.

“If somebody’s not doing the merging the way you do, it’s not because they’re bad people,” he said. “It’s because they have a different idea on how this should happen.”

ON THE SAFE SIDE

A late merge doesn’t happen naturally. Drivers need to be taught how to do it and need on-site directions, usually signs.

That’s why Bob Kramer, president of Wilson’s Driver Training School in Robeson Township, tells his students to move over as soon as they can safely do so if they’re not told otherwise.

“If there’s specific instructions that make that clear, that works great,” he said of late merging. “If there’s not, you’re relying on other drivers to figure that out.”

And it only takes a handful of angry, inconsiderate or just confused drivers to turn a good merge into a mess, he said.

But what’s most important, Kramer said, is that drivers focus on doing the right thing themselves, not on what they may perceive as others doing the wrong thing.

Not letting someone into the lane who you feel skipped ahead isn’t going to make the traffic disappear and may lead to road rage, he said.

“It’s always going to be tempting to teach someone a lesson,” Kramer said. “But it’s never going to be a good idea.”

By LIAM MIGDAIL-SMITH, Reading Eagle