How come my highway is 6 lanes in one direction morning and night?

[yesthattom]

The Tappanzee bridge (connecting NJ to NY) is 8 lanes wide. However, in the morning it is 6 lanes going to NY and in the afternoon it is 6 lanes going the opposite direction. Shouldn't that be 12 lanes? No, because they move the barrier over during the day.

Here's an article about the "zipper machine" that does the work. (The pictures are from a highway near Richmond, VA).

Zipper Machine on I-95



Watching this machine in action is one of the great pleasures in life. It is a testament to out-of-the-box thinking.

Comments

[awfief.livejournal.com]

I love that zipper machine. it's awesome.

[crs.livejournal.com]

We've had ours in Boston for years :)

[awfief.livejournal.com]

yeah, but the Boston one just makes the lane an HOV lane or not. it doesn't actually make more northbound or southbound lanes.

[crs.livejournal.com]

Actually, it does - it makes an HOV lane out of one of lanes from the other side of the road.

[awfief.livejournal.com]

If you're talking about the one on I-93 south of Boston, there's a fixed concrete barrier in the middle, so that's not possible. Is there another one you're thinking of?

[crs.livejournal.com]

The entrance to the HOV lane takes you to the other side of the concrete barrier.

[awfief.livejournal.com]

ahhh, I knew there was something I had to be missing, otherwise the moving barrier was just a "yes HOV lane / everyone gets to drive" kinda thing.

Spatial things are not easy for me. :)

[pir.livejournal.com]

Most places just put lights above the lanes and move the entrance sections :)

I've seen the one in Boston running, though, they're funky.

[yesthattom.livejournal.com]

Changing the lights is fine for short distances or straight bridges. The Tappan Zee is a very long bridge with curves and twists.

They are also safer: 'The barrier is comprised of segments about 5 feet long, with strong interlocking steel brackets that hold the segments of the barrier together, so that it can "flow" through the Zipper Machine as well as have linear connectivity if a motor vehicle collides with it. Jersey'

A car can crash into the barrier and be stopped.

[cyan-blue.livejournal.com]

Eerie, I was just for some reason thinking about that zipper the other day... not really for a specific reason, either!

[vito-excalibur.livejournal.com]

Hahaha! That is SO COOL! Had never heard of it! Thanks!

[emboline.livejournal.com]

OMG! OMG! How "Big Machine" geeky is it of me to think this is one of the coolest things I have ever seen AND I want to watch it one day?

[jayeye.livejournal.com]

Now you know what to get me on my birthday!

[dossy.livejournal.com]

Ah, I did the TZB commute for a few years - I'll be the first to say that I'm glad I no longer do it.

Although, riding along side the zipper truck as it was moving the barricade was great: no traffic in front of you, since the lane is being created in-situ for you! ZOOM!

[ceo]

That's the kind of zipper machine they use for temporary projects. The Boston machine is this big yellow enclosed thing, that is actually oriented diagonally (the wheels are pointed about 20° out of line with the vehicle), so it looks REALLY STRANGE coming toward you. I believe there are wires embedded in the pavement to guide it. First time I saw the barrier on the TZB, I figured out what it was despite never having heard of a zipper barrier before.

Problem with the things is they do tend to chew up the pavement after a while.

[gravitrue.livejournal.com]

I heart the TZB zipper.

[geeksdoitbetter.livejournal.com]

~claps~

you rock!

i was pondering last week, how they move those barriers. i never would have guessed it was a huge machine