Hi,
Can Synchro model a Diverging Diamond Interchange? Is there an example of one?

Thanks
Shankar

Yes Shankar

We can model a DDI using Synchro. We have to direct the flow onto the opposite side of the street using one way links. So all the each and every approach and exit should be considered as a one-way link. For example you would have two one ways links for east leg of the intersection. etc..

All the best...

No it can't. The diverge points behave as unsignalized intersections and cars will not enter those sections. That can be changed by changing the global parameter to allow vehicles to block intersections, but that's a whole different mess.

I've not tried it myself, but I think you probably could using the one way links in the manner SK described.

quote:

Originally posted by Eric Royer:
I've not tried it myself, but I think you probably could using the one way links in the manner SK described.

Try it for yourself. I thought it would work, and so did ODOT staff. It's the diverges that screw things up. Cars won't enter the "unsignalized" intersection.

I don't see why unsignalized intersections allowing vehicles to block the intersection would be a problem. If the unsignalized diverge node is too close to the signalized crossover intersection, move it further away and just run two parallel one-way links to where you want them to flare out and use bend nodes.

Unless you're just analyzing the surface street, wouldn't it be better to use another program? (CORSIM, VISSIM, etc)

The problem is that if you allow them to block one intersection, you allow them to block all intersections since it is a global setting. This becomes a major problem if you have oversaturated conditions or if you are modeling an interchange with overcapacity ramp meters. But yes, you're far better off modeling in VISSIM. On the other hand, if you're trying to interconnect signals along the crossroad, we've modeled them in Synchro first to get the bandwidths and offsets and then transferring the timing into VISSIM.

It's not that Synchro doesn't have its place, but my point is that it's not the ideal software to model DDIs and extract MOEs for the interchange.

Besides, one of the most unexpected benefits of a DDI is its improvement in freeway operations at the merge point when compared to a diamond or SPUI, and for freeways, Synchro doesn't really do a good job.

Entering a blocked intersection isn't a global property. You can "Set All" under Options->Network Settings->Simulation, but you can also set it for individual intersections and lane groups under a specific node's simulation window (F10). It's not quite halfway down the list as a Yes/No in the Enter Blocked Intersection row.

Hope that helps

It certainly helps the intersection itself. Though my previous comment about the freeway merge still stands.