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Author Topic: Roundabout and Rotary Interchanges  (Read 18211 times)

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Offline Haljackey

Roundabout and Rotary Interchanges
« on: November 26, 2011, 03:26:56 PM »
Section 8: Roundabout and Rotary Interchanges
          

Roundabout interchanges are often used when there's is not much room (speaking in terms of space and budget). Roundabout interchanges are quite common in the UK and in continental Europe it's not an uncommon interchange type. The downside is however that these interchanges get quickly congested, but still it does handle traffic better than an at-grade intersection.

Roundabout interchanges are unique in the fact that they can be used as junctions with both arterial roads and other freeways. This makes them a useful choice with roads that may eventually be upgraded to freeways.

Rotary Interchanges involve no grade-separation at all, because they're entirely on the ground level. They act very similar to standard roundabouts, but are much larger and built to freeway standards.

8.1 Basic Rotary Interchange
8.2 Standard Roundabout Interchange
8.3 Full Roundabout Interchange


Back to the Table of Contents

Offline Haljackey

Re: Roundabout and Rotary Interchanges
« Reply #1 on: May 07, 2012, 11:59:32 PM »
Section 8.1 Basic Rotary Interchange (Created by riiga)

Start off by drawing two roads like a plus sign. I used 21x21 tiles.


Then draw the real roads, using the plus signs as a guide.


Use the RHW-4 starter pieces so that the roads become RHW-4 and are in the right direction (like in a roundabout).


Plop 8 smooth inner curves.


After completing the previous step, it should now look like this.


Now, add 4 90-degree MIS curves. Make sure they are in the right direction. (Use the DrawPaths cheat if unsure)


Plop 8 A-type inner ramps so that they connect to the MIS curves.




You're now done!


If you like, you can add some decorations. This is my final result.

Offline Haljackey

Re: Roundabout and Rotary Interchanges
« Reply #2 on: May 08, 2012, 12:00:23 AM »
8.2. Standard Roundabout Interchange (Created by mrtnrln)

Roundabout interchanges are often used when there's is not much room (speaking in terms of space and budget). Roundabout interchanges are quite common in the UK and in continental Europe it's not an uncommon interchange type. The downside is however that these interchanges get quickly congested, but still it does handle traffic better than an at-grade intersection.

Today we create a Standard Roundabout Interchange (or technically speaking, a Dual-level Roundabout/Rotary Interchange), where one freeway continues, while the other intersects with a roundabout. This will require at least RHW v3.2, although I'm using RHW v.4.1 here.

1.  First we construct two RHW's:


2.  As you can see, I put some 1x1 road tiles around the RHW, which are marking an area of 12x12 tiles. This area will be demolished:


3. Then lay at the ends of the RHW some OWR stretching four tiles


4. Connect the ends of the OWR. Make sure the roundabout goes in the right direction.


5. Now demolish a 2x2 area at two opposite stretches of RHW and replace them by OWR like this (again, make sure the OWR is pointing into the right direction):




6. Now make a ERHW-overpass with the other two RHW-ends over the roundabout.


7. Then place some ramps at both ends of the overpass:


8. And finally, connect the MIS with the roundabout via OWR:


9. There you have it, a Standard Roundabout Interchange.


Variations for more experienced RHW-users
1. You can use RHW-6 at both ends of the overpass and use a C-type ramp or a RHW-6S/8S-Splitter instead of a A-type ramp.




2. You can also use on-slope transistions for the RHW- overpass.


Offline Twyla

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Section 8.3. Full Roundabout Interchange
« Reply #3 on: July 10, 2012, 07:20:17 PM »
Section 8.3. Full Roundabout Interchange

For those desiring an efficient AND compact interchange between two RHW routes, nothing fits the bill like a Full Roundabout.  Although there is weaving on the roundabout (even tighter on the A1 variant shown at the end), the roundabout itself acts as a collector/distributor for the entire interchange - only requiring one off-ramp and one on-ramp with no weaving on the throughways themselves.  Even this double-C/D Monster of a 10S x 10S Full Roundabout fits entirely within a Small City Tile.



STEP 1: Positioning Markers
Plop a small marker precisely where you want the two routes to cross.  To demonstrate the versatility of this tutorial, I've opted to have an RHW-6S (2-tile network) interchange with an RHW-6C (3-tile network), thereby using a 2x3 intersection marker.  (The Monster pictured above uses a 6x6 intersection marker.)   Whatever interchange you can dream up, the only difference in construction is the size of the interchange marker.

Place five marker tiles coming diagonally off each corner of your intersection marker to help guide you on the next step.



STEP 2: Roundabout Perimeter
Drag diagonal RHWs immediately adjacent to your outermost marker tiles.  Make them as long as you can without any of them actually connecting to each other - this forms the core of our C/D-type roundabout.  We'll be using RHW-4 Type B1 Diagonal ramps to access this and they can be a touch finicky, which is the reason for the extra length.



STEP 3: On-ramps and Off-ramps
Now we place all of our aforementioned RHW-4 Type B1 Diagonal ramps.  I've demolished some of the marker tiles to better show how every MIS ramp lines up directly with the second closest marker.  Although the proximity between on-ramps and off-ramps causes some weaving, this is restricted entirely to the roundabout itself leaving the main throughways congestion-free.



STEP 4: Coming Full Circle
Now we close in gaps to complete our C/D roundabout.  I've placed additional markers to illustrate how the inside curve should extend two tiles beyond the width of the main carriageways - this is needed to preserve the RHW-4 overrides when we place our overpasses.  (It also helps to more closely resemble the circular shape inherent to roundabouts.)



STEP 5: Main Carriageways
Now we place the elevated transitions for our main carriageways.  The extra tiles we allotted in the previous step reinforce the overrides, enabling us to place the transitions as close as we like.

Due to RHW only having L0 and L2 heights at this time, one of the routes needs to return to ground level.  Simply for aesthetic reasons, I opted for the 'smaller' 6S carriageway - two overpasses in succession make it a tad bumpy for your Sims, so choosing the route with the lower capacity/traffic "minimizes the inconvenience".


STEP 6: Providing Access
Now we need to provide access to the C/D roundabout.  Plop MIS 45-Degree Curves coming off each of the roundabout's ramps, then place the appropriate 45 ramps coming from the main carriageways - either Type B (same RHW width) or Type E (next size larger).  For the 6C shown below, this means either a 6C-Type B or an 8C-Type E.  (The latter, of course, provides for acceleration/deceleration lanes for a bit more realism.)   

NOTE!:  There is presently a minor glitch with several of the RHW Type E Entrance Ramps whereby the preview is offset by one tile, so be sure to take this into account when placing these ramps.


STEP 7: Buttoning It All Up
Drag the main RHW Tool to button everything up - though the ramps will likely need 45 MIS Puzzle Pieces (found with the RHW Starters) - and now your Sims can enjoy congestion-free motoring throughout their world!  Compact enough that (unless you make The Monster) you still have room for four surface interchanges within a Small City Tile.



OPTIONAL APPROACH: RHW-4 A1 Diagonal Ramps
For those wanting to squeeze this interchange down a wee bit smaller, you can utilize the RHW-4 Type A1 Diagonal ramps (and A/D ramps on the carriageways) to tuck the on-ramps and off-ramps in tighter.  It's a bit trickier to get A1 ramps positioned correctly (as they butt directly against one another) so you may want to practice with the original interchange before attempting this second one.

Offline melinuxfool

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Re: Roundabout and Rotary Interchanges
« Reply #4 on: August 28, 2012, 04:06:10 PM »
Interesting. Being from New England, I wanted to join and show what I came up with. I live in Maine, a small area, and even we have about a dozen rotaries or so. Massachusetts probably has around a hundred of them.

This one is as close as I could come to approximating what I think of when I think of a rotary.


Close-up of an entrance and exit


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Offline Kitsune

Re: Roundabout and Rotary Interchanges
« Reply #5 on: August 28, 2012, 05:20:34 PM »
I shall never forget Barbados 4 to 6 lane highway... 90km/h speed limit and round abouts.. standard ones too... at all intersections. And people were going 100+ through them. Was darn scary trying to merge into one.  :o
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Offline melinuxfool

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Re: Roundabout and Rotary Interchanges
« Reply #6 on: August 28, 2012, 06:45:41 PM »
I shall never forget Barbados 4 to 6 lane highway... 90km/h speed limit and round abouts.. standard ones too... at all intersections. And people were going 100+ through them. Was darn scary trying to merge into one.  :o

Reminds me of this one in Portsmouth, NH.

http://www.flashearth.com/?lat=43.072994&lon=-70.780711&z=19.1&r=0&src=msa
I think this one is about a quarter of a mile "long", that is, if you drive all the way around it. It's a fairly large (and fun, imho) rotary. I had a 4x4 truck, high off the ground and I could navigate the circle in that thing at about 72 km/h. I'm sure 80 wouldn't be that dificult in a small car. The official speed limit is about half that, however.


Offline Haljackey

Re: Roundabout and Rotary Interchanges
« Reply #7 on: August 28, 2012, 07:42:22 PM »
The craziest Roundabout/Rotary that I've been on was en-route to Cape Cod in Massachusetts, USA.

Recently it was upgraded to a (rather odd looking) interchange to increase capacity and make it more efficient: http://goo.gl/maps/hjKuV
-If you find that location in Google Earth, you can go back in time to see what existed beforehand.

Offline tvrcars

Re: Roundabout and Rotary Interchanges
« Reply #8 on: November 22, 2013, 07:22:12 AM »
founds this a good while back and thought i should share it, it shows how to make roundabouts and alot of other stuff for RHW

http://www.youtube.com/user/Asteconn?feature=watch

Offline AsimPika3172

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Re: Roundabout and Rotary Interchanges
« Reply #9 on: December 24, 2020, 03:53:17 AM »
7 years later... Sorry for necrobump... Just see nice roundabout for RHW! I will try it now!  :thumbsup:
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