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Single Point Urban Interchange

THIS INTERCHANGE REQUIRES TRAFFIC MANAGER. To make it work like in the video, we're going to have to set up a timed light. This one is really really simple though. I actually made it as sort of introduction to using phased intersections, since this is the easiest one of all. It's just one light to set. And it's a great example of how a proper light sequence can dramatically increase efficiency.

You can read how to do that here, or watch a video of how I set one up, and if you have any difficulties, leave a comment here, and I'll try to answer it. Give it a try!

THE SINGLE POINT URBAN INTERCHANGE

The Single Point Urban Interchange, or SPUI, is an improvement over a traditional diamond interchange. By moving the intersection of the minor road with the ramps to a single point over the highway, the design both saves space and allows access to be controlled by a single set off lights. This also allows left turning traffic in opposing directions to turn simultaneously without crossing paths.

WHERE TO USE IT

The SPUI is a service interchange, for connecting surface roads to your highways. It's an excellent design for handling moderate traffic. It's the smallest and cheapest interchange design in this game, and the easiest to set up properly with traffic manager.

There are larger, higher capacity designs, like the Diverging Diamond or DCMI, which reduce the number of phases further, or get rid of them alltogether. But they really aren't necessary except for large, dense, or industrial districts.

If you're using this asset, first make sure the ground is absolutely flat with the terraforming tool. Place it where you'd like and connect it to your highway and surface streets. Also, if you're using road anarchy, make sure node snapping isn't turned off. Next, we'll use traffic manager to direct it.

LANE CONNECTOR + JUNCTION RESTRICTIONS

The first thing we're going to do is tell drivers where to make their turns, and from which lane. The diagrams I posted of the signal phases pretty much show where all these lanes are going. Right turns, which I didn't show, just proceed freely along the outside of the interchange. I also put up a picture of the lane connections I used. You can use that, and I'll describe it as well.

As drivers approach the highway on the minor (6 lane) road, each lane will be reserved for one direction: the right lane for turning right, the center lane for crossing the highway, and the left lane for turning left onto the highway.

At the two intersections on the outside of the interchange, connect approaching traffic from the right lane to the highway ramp on its right, the center lane to the right lane of the bridge, and the left lane to the left lane of the bridge. For traffic leaving the interchange, connect the highway ramp to the right lane of the minor road, and the single lane from the bridge to both the left and center lanes of the minor road.

At the central intersection above the highway, connect both highway ramps approaching the intersection to the single lane of the minor road leaving the intersection on its left. You can also connect the ramps coming off the highway to the ramps headed to the highway in the opposite direction if you want, to allow U-Turns. Connect the left lane of the minor road approaching the intersection to the highway ramp on its left, and connect the right lane of the minor road to the single lane of the minor road crossing the intersection to the other side of the highway.

Also make sure that drivers on the highway ramp are entering or leaving from the proper lane. Left if they're headed left, right for right. You can use lane connector to make sure cars merge onto and off the freeway smoothly, as I did in the video.

I probably went a little overboard, I put in a bunch of other lane connections that probably aren't necessary.

SETTING UP THE TRAFFIC LIGHT

Right now the lights are in the wrong place. There should be only one light, right in the middle of the interchange. Use "Switch Traffic Lights" to remove the two lights on the outside of the interchange, and place one in the middle.

Now click on "Junction Restrictions". Click on the two intersections on the outside of the interchange, and turn the little symbol of a car rear ending the other green. That tells drivers they don't need to stay back to keep out of the "keep clear" section of the intersection. Since it's not a real intersection, it's just where drivers are making right turns, we don't need them to worry about that, and instead can let them stop at the single light in the middle instead.

Now, we're going to program that light. The SPUI has three phases, first drivers headed across the bridge in either direction are allowed to proceed, then drivers from the minor road turning let onto the highway in either direction. then drivers getting off the highway turning left in either direction.

Click on "Timed Traffic Lights" and click on the central intersection, and then "Setup Timed Traffic Light".

Click "Add Step", you'll notice all the signals for all the lights for all this phase are displayed, and we can change them for red to green by clicking on them. But first, we're going to have to change the light for drivers approaching on the minor road so that it has a seperate left turn signal. Click "Change Mode" twice for those two signals until it displays three different arrows.

For phase one, turn the two forward arrows for the minor road green. You can also set the min and max time for the light to stay green. The game will let the signals with the most cars waiting stay green longer. I'd set it with a low min time. When you're done click "Add", and it will save phase.

For hase two, click "Add Step" again. Turn the forward arrow for the minor road back to red, and the left turn arrow green. Make double sure it's the left turn arrow and not the right turn arrow. Again, click add to save the phase, and click "Add Step" again for phase three. Now turn all the lights for the minor road to red, and the lights the highway ramps green, and add the step. And now we've set all the phases.

Remember to hit "Start" to activate system you set up. I spent ten minutes trying to figure out what was wrong with my lights when I set my first timed light with Traffic Manager before I realized I'd never turned it on.

WORKING?

It should be working now. If it's not, and you can't figure out what's wrong, leave a comment here and I'll try to help you fix it.

So there's your SPUI. Watch how cars handle the intersection and you'll see how much more efficient intersections are when you set the lights up. This kind of thing is at least as important a part of designing an effective infrastucture for cities in the real world. Now, with traffic manager you can do this in the game. Taking the time to do this is really far less time-consuming than building massive networks of fly-over ramps everywhere, it takes up less space, works better, and looks far better and more realistic too.

After the SPUI, there are other, even higher capacity intersections and interchanges we can build, using multiple coordinated lights. Probably the next step up in capacity and complexity would be the Diverging Diamond Interchange, which cuts the SPUI's three signals down to just two.
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=853863115

Check it out.

And thanks for trying out my interchange.