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by **coyttl** on Sat Feb 02, 2013 3:32 pm

..a real-life example of an intersection with more than two rings.

Anyone? Anyone? :drool:

by **vaughn** on Sat Feb 02, 2013 3:34 pm

What is a ring in an intersection :scratch:

Is that a dumb question?

by **EPAC-EPIC-MARC** on Sat Feb 02, 2013 3:53 pm

vaughn wrote:What is a ring in an intersection
Is that a dumb question?

A ring is a group of 4 phases. On a standard NEMA controller Ring 1 contains phases 1 through 4, and Ring 2 contains phases 5 through 8

Ring 1 phases operate in sequence... Phase 1 runs then, 2, 3 4 and back to 1. Ring 2 phases sequence depend on Ring 1 and overlap eachother.

Phase 1 and 2 operate with Phases 5 and 6, and Phases 3 and 4 operate with Phases 7 and 8.

Example below

Spoiler:

Many modern controllers allows for a third or fourth ring for phases 9 through 12, and 13 through 16 respectively. I've yet to see 16 phase intersections in actual use and require the controller to have it's outputs remapped.

Siemens NEXTPHASE software allows for 20 rings, and 40 total phases
Intelight MAXTIME software allows for 16 rings, and 50 phases.

....

....

by **TacomaJoe** on Sat Feb 02, 2013 4:01 pm

I think we have some using phases in ring 3 but it is more for the LINK light rail.

by **coyttl** on Sat Feb 02, 2013 4:02 pm

EPAC-EPIC-MARC wrote:A ring is a group of 4 phases.

The '4' is misleading - you can have 1, 2, 3, 4, or even 15 signals in a ring. I know. I've tried. :)

by **vaughn** on Sat Feb 02, 2013 4:10 pm

Geez, I would have never guessed that. I'm not familiar with controlers or there funktions as far as phases or even what a phase is. I'm getting it tho, a phase controls. Ok, I'm still lost as to what a phase is.
Normally for me to understand I have to read something several times before I get the jist of it and it looks like this will be the case here.

by **EPAC-EPIC-MARC** on Sat Feb 02, 2013 4:16 pm

coyttl wrote:
EPAC-EPIC-MARC wrote:A ring is a group of 4 phases.

The '4' is misleading - you can have 1, 2, 3, 4, or even 15 signals in a ring. I know. I've tried. :)

True, with these controllers theres plenty of room for customizing. But the standard is 4 phases per ring

by **coyttl** on Sat Feb 02, 2013 4:38 pm

vaughn wrote:Geez, I would have never guessed that. I'm not familiar with controlers or there funktions as far as phases or even what a phase is. I'm getting it tho, a phase controls. Ok, I'm still lost as to what a phase is.
Normally for me to understand I have to read something several times before I get the jist of it and it looks like this will be the case here.

A 'phase' is a direction of traffic.

East or West on main street can be 1 or 2 phases. 2, if you then have left turns, as well. (Both lefts would be a phase) This would give you two phases on two rings. This intersection would have the side streets one way going away from the intersection. (Not common, but certainly possible in cities.)

Then you add the throughs and lefts for the side streets, and you have 2 ring, 8 phases. (4 phases on a ring.) Each ring can only have one green on at a time, and co-phases are phases that can co-exist green together.

For example, here's an intersection I'm recreating -

Except for an overlap ('A', which you can ignore for now, it's the right-turn signal), this is a standard 2 ring 8 phase setup.

So, ring 1 would be phases 1, 2, 3, 4,
ring 2 would be 5, 6, 7, 8.
One green can be on in a co-phase group at the same time. Co-phases are 1, 2, 5, 6, and 3, 4, 7, 8.

So, phases 1 OR 2 can be green ALONG WITH 5 OR 6. (NB Left can be green with SB Left or NB Thru. NB Thru can be green with NB Left or SB Thru. And so on.)

A 'barrier' is between phases 2 and 3, and 6 and 7 - a barrier means that all signal have to go red. So before ANY side-streets are services, ALL NB and SB lanes have to go red. Then repeat the process for the four EB and WB phases.

Rinse, repeat as necessary.

The 'A' in my diagram is an Overlap - it can be GREEN through two CONFLICTING phases - Phase 1 and Phase 4. Phase 1 and 4 can NEVER be green at the same time, but O/L A can be.

And that's it, in a nutshell. :thumbsup:

It's really shortened, but that's the gist of it.

Newer controllers can have more than two rings, and the purpose of my post is that.. I'm curious to see this in operation somewhere. Like Joe said, his city uses it for Light Rail - which I honestly hadn't thought of before, but makes sense.

by **mikerm** on Tue Feb 05, 2013 9:03 pm

so yeah, my head just exploded trying to understand all of that... :shock:

by **2070** on Tue Feb 05, 2013 9:18 pm

coyttl wrote:For example, here's an intersection I'm recreating -

Except for an overlap ('A', which you can ignore for now, it's the right-turn signal), this is a standard 2 ring 8 phase setup.

Add a 5th leg and exclusive Peds!! Then its a party! With Phases 9 and 10.... :yes:

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