I hate the zipper merge. Time to stir the pot

wae said:

Typically, I want to make sure I'm in the right lane as soon as is feasible.  I don't want to force my way over three miles before the lane ends, but if I know I need to be in a particular lane anyway, it's not the left lane, and there's an opening, I'll go ahead and take it.  As we approach the closing of the zipper, I'll leave a couple car lengths so that folks can go ahead and get over.  Ideally, every car in the continuing lane lets in 1 car from the ending lane, and we all get there without too much delay.  What makes the vein in my forehead pop out, though, is when I'm leaving copious space in front of me, the closing lane is basically empty for about 10-15 cars back, we're 4 or 5 cars from the closing of the zipper, basically at a standstill, and people blow past me, usually on the right, to get right up to the close and come over.  I see that on the on-ramps during heavy traffic all the time around here.

I have nearly been sideswiped and have seen near-sideswipes of other people a few times by folks that decide they don't want to wait in the line of cars and drive in either the shoulder or the center turn lane - at speed! - for a quarter mile or more.  That type of behaviour is far more dangerous than waiting until the last minute on a zipper merge.  You've got someone who is either at the point where the not-a-lane becomes a lane or they also decide that they're going to use the not-a-lane, they pull in to it not expecting or not being able to see a car barreling along at fifty miles an hour, and things get really hairy really fast.

This is how it is supposed to be done.  In between the first "lane closed ahead" and the actual zipper, you are to get in the correct lane when it is safe and feasible.  If there is enough traffic that you are stopped or significantly slowed, you are supposed to fill both lanes to the zipper and then take turns.  But when everyone chooses the open lane immediately, that's when braking urgency increases exponentially, and that's when you hear about an 18 wheeler accordion-folding 10 cars because it couldn't stop.

One of the most brilliant revelations I had while in a chopper observing traffic is that it has little to do with the volume of traffic.  You would watch, and 5 miles up the road you would see one or two brake lights for a split second.  Then 4 cars behind them would put on their brakes for 1 second.  Then 10 cars behind them for 3 seconds.  It becomes this cascade of "oh crap" braking until the cars right under the chopper are at a full stop.  Meanwhile, 5 miles ahead the road is moving just fine.  One person touching the brakes and one person following a little too closely for comfort causes a 5-mile backup.

Zipper merging works great when everyone uses proper zipper merge technique (spoiler alert that never happens).

Zipper merges also suck when you're towing a trailer, which is usually why I'm on a highway in the first place.

Curtis73 (Forum Supporter) said:

One of the most brilliant revelations I had while in a chopper observing traffic is that it has little to do with the volume of traffic.  You would watch, and 5 miles up the road you would see one or two brake lights for a split second.  Then 4 cars behind them would put on their brakes for 1 second.  Then 10 cars behind them for 3 seconds.  It becomes this cascade of "oh crap" braking until the cars right under the chopper are at a full stop.  Meanwhile, 5 miles ahead the road is moving just fine.  One person touching the brakes and one person following a little too closely for comfort causes a 5-mile backup.

I forget the name for it but this ripple effect is widely studied by traffic engineers. It's not even caused by following too closely, a lot of people hit the brakes for no reason like to read signs or if the road changes direction slightly. I lose my mind when people hit the brakes going uphill.  I've also been in a traffic jam caused by a single RV going 35 on a 65 freeway.

In reply to j_tso :

Yes... or you have trucks going up a mountain in the right lane at 35 mph, but the one behind is able to muster 35.5 mph, so they pull out to pass and ruin it for everyone.  I'm a CDL driver, and I don't do this.  I totally get that you don't want to lose momentum, but 1/2 mph?  C'mon.

The name for that ripple effect is eluding me too.  It was something like inchworming.  The traffic guy I knew called it a bungee

Curtis73 (Forum Supporter) said:

In reply to j_tso :

The name for that ripple effect is eluding me too.  It was something like inchworming.  The traffic guy I knew called it a bungee

concertina?

https://en.wikipedia.org/wiki/Accordion_effect

In reply to eastpark :

I always called it the inch worm. 

We can agree that in light traffic, we should all get in line early so we can continue at the legal speed limit.

How about this:  If you are in the lane that is closing, and you have to come to a stop to change lanes, go to the front of the line and do the a b a b thing, because stopping farther back accomplishes nothing.

Zippers don't even zipper merge all that well unless all the teeth are exactly the same size and distance apart...

No matter what, losing lanes is gonna suck and there's no way to keep the same volume of traffic moving through at the same speed.  If they could, we wouldn't NEED more than one or two lanes instead of three or four or five.

I had no idea what a zipper merge was for years since I grew up driving on Atlanta's highway. Depending on the part of town, a zipper merge may form naturally. But most of the time merging into thick traffic is more like a game of chicken. But on the top end near 400, it is damn near apocolyptic. Like this but with upper middle-managers in huge SUVs and Audis:


 

Nowadays I just leave gaps all the time in front of me and let people in. I'm going to get stuck at a light or somewhere else on my drive, I don't care anymore about getting there fast. Not worth getting shot (which keeps happening here).