Harbor XL by Asterian
UIM by Altiris
Highway Intersect by Hyperwolf
8 lane road by Pharmist
6 lane road by Pharmist
I dont have any of that new fangled technology like discopolis uses to make vids so i took pics instead.
Besides this process is a multi day process.
My example below took me three days to complete.
You could perhaps try a smaller version.
i leave it up to you.
But you may simply gather ides from the processes i used to make even better systems!!
Oh and like it if you do..... this took another three days to write!
Make sure that the land on your map is deep enough to have sunken roadways.
I am using the Great lakes Map.
In the picture above I have terraformed the land to be higher than normal then bulldozed all of the trees as i find them confusing.
I recommend doing this no matter what map you are using as this will ensure a perfect flat surface on which to build.
This is of course provided you know how to terraform correctly. i extend my perfect flat layer all the way to the coast line.
This creates some rugged cliff-like edges, that are not the most appealing thing in the world, but I have a way of fixing that later.
Using whichever roads you wish, draw out your highway system that you wish to be underground.
I have used the eight-lane highway by Pharmist as it is nice and wide.
Also make a point of using the straight road tool as you may find it to be a huge mistake later on if your roads are not straight.
This tutorial is focusing on using a below ground straight road-grid system which is very complex as it is, curved roads may be possible too. BUT HARDER
Drawing the roads is very easy.
Just create 2 parallel roads close together and extend them from where you want the first and last entrances.
In my picture above I have done this, but also created another highway that intersects at cross angles. You can do this too.
The reason there is 2 roads for each highway, may not be obvious to all, so ill make a point of saying that it is so i can turn them both into opposite one ways later on.
You may also notice I have placed some small avenues around the highway system.
You should ignore those at this step and only focus on the intersecting highways for now.
Here you can see how I have extended the complexity and length of the highway system.
This is to highlight that many configurations are possible.
One very important thing to remember is to leave a bit of space near the ends of each road to build entry/exit points later.
Notice I did not extend the roads to the edges of the map/land.
Now back to that small avenue....
I recommend small avenue but use your preferred choice to make an outline of the highway system as i have done above.
Notice how all the free ways join onto the small avenue at their ends across the whole system.
Also note that the sections in between the highways do not join onto the system. This creates a virtual rectangular island.
Make certain that you leave a small gap between the highway and the small avenues, but not too small either!
Closely examine the images!
Now the fun part!
Place high density lots all around the small avenues as i have done in the image above.
You can use the liner placement tool if you wish, but just be sure that any gaps are symmetrical.
Notice in my image that wherever there was not enough room for that last plot, I have made sure that the opposite side of the highway matches.
These plots are just for controlled measurements later on.
It is best to build these without a town hall placed so that they don't fill up with residents. it doesn't matter though as they all get deleted later on.
This next step is a pain in the donkey but......
Take a good look at the picture above.
Notice what I have done?
I have removed pairs of plots from select locations around the highway system.
These gaps will be where I one day build my overpass bridges over the sunken highways.
This is not all I have done.
I have built small sections of small avenue on either side of the gaps where the plots once were.
Try to make these exactly perfectly straight and as close as possible to the remaining plots.
You can now use this process where you want bridges over your sunken roads.
Now, join up all the small avenue sections of road so they they extend completely around each section of plots.
Also be sure to link all the plots together on the side furthest away from the highways...then delete the section closest to the highway.
I forgot to take a picture of that last bit so really study the above example where the plots link to each other and notice the gaps near the highways sytem.
The next image might make this easier to understand....
In this step, you will delete the highways you built as they were only guides.
So much of this tutorial will be simply guides. it is a complex process.
But one that which taken one small step at a time, will be very easy to follow.
Notice how you can still clearly see where the highways will eventually go as well as where their overpasses will be!
Here is the hardest part and a perfect time to save your game in case you screw up!
Using the IN-GAME HIGHWAY TOOL, you will re-draw your highway system.
You MUST use the STRAIGHT road feature when building this highway. This is part of the UIM mod by Altiris.
When you select the highway from the thumbnails, it will auto-select curved roads. CHANGE IT.
It is not as simple as you may think.....
You need to start by clicking on the small avenue at the beginning/end of one of your freeways.
In the pic above, see how my sunken highway begins at ground level from the small avenue on the left?
Start from the Road....
Using the shift key change the depth of the highway down to its lowest level but don't let it become a tunnel!! That is very important!
Before you click to place the first waypoint, notice that to the right is the gap that will become an overpass.
I have extended my downward slope up until this point and then clicked ONCE to end the slope.
You can see this as the highway slopes down then suddenly comes out flat.
You will need to extend this flat section of highway to the other end of the system.
At this other end you want to click again a similar distance before the end to create another waypoint.
If the highway becomes a tunnel at any point, try to very gently raise it slowly to keep it as a highway. You want to keep the highway as flat as possible.
This will allow you to slope the road up the small avenue on that end.
End the highway here. The start and end should be mirror images of the above images.
You should now have a highway that slopes down, goes out straght and slopes back up again.
You will notice that the ground has magically terraformed around the highway.
But at this point it will be very messy.
Repeat this process for the second roadway and any other highways you have in your system.
Also it should be worth noting that the highway intersect mod by hyperwolf should be used to allow the highways to intersect.
DONT WORRY ABOUT THE MESSY TERRAFORMING SO LONG AS YOUR ROADS ARE FLAT AND EVEN.
IF YOU ARE UNSURE, DO NOT ACCEPT THE ROAD AS THERE IS NO UNDO, UNCLICK THE WAYPOINTS AND TRY AGAIN.
See here I have done step 9 for all my other highways.
But I also did this for the overpasses. This too is very important.
Do it now too!
The magic of this next example was acheived by another mod....
you must have harbor XL mod by asterian
In this mod there is 3 plazas which can be located with all the harbor XL stuff inside manufacturing/special menu.
I used the dark grey plaza.
This magical plaza has special terraforming abilities.
by placing it in between all the higways, see the pic above..... it will lower the ground either side to be perfectly even with the roadway.
this leaves a nice brick wall of the small avenue on the side for drivers to look at.
fill in all the gaps where you want the road to sink using this plaza.
Delete all your highways again!!!!
In my example above, I have deleted all the sunken highways. Notice that the plazas i placed all around them are still present.
To the left of the above image you can see that I have begun to fill in the gaps left by the deleted highways with more magic plaza effectively creating on huge plaza.
Do this for the enitre system.
You might notice that some part of the plaza are higher and lower than others.
We will need to straighten that out to make the floor completely uniformly flat, but first make sure you have fill in all gaps with magic plaza.
Now ONE BY ONE, delete the raised sections of plaza and replace it with more magic plaza.
The process is tedious due to some constant menu changing.
but it is essential....
You should end up with the result of the next image.
Now you can go ahead and delete all the plazas.
make sure you get it all! even tiny bits in corners.
It should look like above when done.
Now add your final highways roads.
I have once again used the 8 lane road by pharmist as i can turn them into 8 lane each way roads. but you can use what you like.
dont join them to the outside yet, just place them nice andstaright in the sunken part of your system.
See what i did above.
Using the bridge tool of the same road you have used for your highway, link your sunken highway to the small avenues.
See above how the small section of bridge flows down to meet the sunken road.
If there is not enough room for the bridge to complete, join the two roads of your sunken highway together a little further back and delete the excess to create a longer slope for the bridge.
I did this in the pic above.
You can see the two roads linked. Once the bridges are built, delete this link.
Using another Pharmist mod: 6 lane highway BRIDGE VERSION, i link the over pass to the small avenues.
This pic says it all.
There should be enough space for the bridge to simply meet on both sides and be perfectly flat. Just join it.
As you do this, the land will re-terraform around things.
Dont worry as we can use magic plaza gain later.
REPEAT FOR ALL....
Looks nice doesnt it?!!
Either delete all the plots and replace them with what you wish or keep them as housing developments.
I chose to replace them with a red plaza.
HERE ARE SOME FINALE PHOTOS....
I linked all the roads together....
it looks nice at night too.
I began to make a bridge.....
THIS CITY WILL BECOME MY NEW CITY JOURNAL SHORTLY.
It is also replacing my One Map Challenge City of Alpha Beta as this city crapped itself and wont let me in.