I am comparing different interchange types using the delay/veh for the total network. I'm looking at a SPUI, TUDI, and two Clover Leaf designs. The network I have setup is only the interchange (including ramps and free flow through movement). The volumes are high because I am modeling year 2035.

I am getting results of around 6 min/veh. This seems high to me since the network from end to end is less than 1.5 miles on each road.

How does the delay/veh relate to the average vehicle in the network? Do my results really mean that it will take 6 minutes for the average vehicle to pass through the network? I'm doing a write-up on the analysis for a non-technical reader so is there a different SimTraffic output that would make more sense?

Which delay report are you looking at? Make sure it isn't the Total Delay in hours. Is the speed limit in Synchro set right?

If you are looking for the travel time and delay of the surface street through the interchange, the Arterial LOS report would probably be best. If you haven't added street names to your links, you'll need to before you can get the arterial report to work right.

If you're looking at flow on the interstate/highway through the interchange, you probably want to use another simulation package.

Good luck!

I'm unfamilar with the TUDI interchange is this just a tight diamond? ...the only thing that came to mind was the show "Facts of Life"

a delay 6 minutes for a mile and a half might not be unreasonable, it depends on your arterial speeds. Over a mile and a half, it represents a reduction in speed of about 15mph.

some things to look for:

watch your simulation and see of there are areas where/if congestion is backing up off the network.

The ramps should be modeled all the way to the gore points; if it backs up near this point you're running the risk of impacting mainline flow, as well as creating opportunity for rear end collisions.

Use your Link O-D to prohibit interchange U-turns, unless you have data for this number.

I typically set ramp speeds to 45mph to estimate the difference between mainline speeds, and urban street speeds.

Thanks for the comments. I got the clover leaf designs to work better. The problem with the SPUI and TUDI is that the volumes are just too high for the signalized intersection. Eric, TUDI stands for tight urban diamond interchange. It's similar to a regular diamond but the ramps are spaced closer together and the two signalized intersections at the ramps operate as one signal; no vehicles get trapped on red between the signals.

ah...never heard them referred to as tight "urban" diamonds...we simply call them tight diamonds.

There has been a lot of buzz recently regarding the diverging diamond / double crossover diamond interchange, stemming from the opening of the SR 13 / I-44 interchange in Springfield, Missouri. Is this kind of interchange something that work at your location?