Traffic flow on 15 Different 8-way Intersections (and alternatives) Measured, Ranked and Compared.

UPDATE: Feb 2021: Gotten more views over the last few weeks & loads of people have mentioned that improved lane mathematics would have greatly improved some of these intersections. This is true, but then I would have had to make structural changes to the intersections and my intention was to test the intersections exactly as intended by their creators, although I did use TM:PE to manage lane changing.

In this video I rank and compare 15 different 8-way intersection designs (including two alternatives) to see how they perform under 3 different initial traffic conditions, namely, "light", "Moderate" and "Heavy" traffic scenarios and ultimately find the best.

To do this I used Cities: Skylines, Traffic Manager President Edition (TMPE) the Mass Transit mod, Network Extensions 2 DLC and a small custom mod I wrote to count vehicle numbers over time.

Chapters:
0:00 Intro

0:15 1. "Standard 8-Way, no Traffic Lights"
0:59 2. "Standard 8-Way, Traffic Lights"
1:30 3. "Large Roundabout with slip lanes"
2:15 4. "8-way magic roundabout" by "Tremor"
2:55 5. "8-way Double-Roundabout" by "RichAntDav"
3:39 6. "8-Way Highway Interchange" by "RobinSinouh"
4:22 7. "8 way snowflake interchange #2 (double cloverleaf)" by "3nƒ0я¢3я"
5:28 8. "8-Way Quad Roundabout v2" by "RichAntDav"
6:17 9. "8-way Ultra Interchange" by "bubbac2005"
7:08 10. "8-Way Double Cloverleaf" by "RichAntDav"
8:03 11. "8-Way Highway Intersection" by "Jazumojo"
9:04 12. "8 Way Highway Interchange" by "FightBiscuit"
10:09 13. "8 Way Interchange" by "General Grievous"
11:11 14. "Four 3-Way and one 4-Way intersections"
12:17 15. "Four 4-Way intersections"
13:23 Outro

Details:
1. Standard 8-Way, no Traffic Lights
Size: 10x10
Cost: 6,400
2. Standard 8-Way, Traffic Lights
Size: 10x10
Cost: 6,400
3. Large Roundabout with slip lanes
Size: 58x58
Cost: 18,240
4. 8-way magic roundabout
Creator: Tremor
Size: 56x56
Cost: 47,932
5. 8-way Double-Roundabout
Creator: RichAntDav
Size: 64x64
Cost: 108,530
6. 8-Way Highway Interchange
Creator: RobinSinouh
Size: 64x64
Cost: 106,880
7. 8 way snowflake interchange #2 (double cloverleaf)
Creator: 3nƒ0я¢3я
Size: 92x92
Cost: 170,010
8. 8-Way Quad Roundabout v2
Creator: RichAntDav
Size: 64x64
Cost: 98,300
9. 8-way Ultra Interchange
Creator: bubbac2005
Size: 64x64
Cost: 139,230
10. 8-Way Double Cloverleaf
Creator: RichAntDav
Size: 84x84
Cost: 190,540
11. 8-Way Highway Intersection
Creator: Jazumojo
Size: 188x188
Cost: 460,090
12. 8 Way Highway Interchange
Creator: FightBiscuit
Size: 180x180
Cost: 394,009
13. 8 Way Interchange
Creator: General Grievous
Size: 100x100
Cost: 251,000
14. Four 3-Way and one 4-Way intersections
Size: 72x72 (just intersections) or 130x130 (total)
Cost: 199,750
15. Four 4-Way intersections
Size: 80x80 (just intersections) or 150x150 (total)
Cost: 237,240

Notes:
The first 13 intersections are not strictly in order of performance, because we would really need 3 different sets of rankings (one for each scenario type). This is because while one intersection may perform better than another at the "medium" traffic level, it could perform much worse at the "High" traffic level. An example of this would be no. 8 which, because of it's reliance on roundabouts, it performed well at the "medium" level, but collapsed at the "high" traffic level and had worse performance than earlier intersections. So the ranking is not strict and is really just my subjective opinion.

No.14 & 15 are made up of some 3-way & 4-way intersections I had, & are there to illustrate why we don't see these things in real life.

Thanks:
To all the intersection creators, credit & links to their creations above.

[pwhnckexstflajizdryvombqug]

The interchanges you used to make the last one are called "Bel Geddes" interchanges, ultimately I think they work the best and is probably the most realistic solution, especially since you can build a city in the middle of it.

[What_Other_Hobbies]

Summoning biffa to do some lane mathematics.

[sadgiraffe]

If you need an 8 way intersection it time you replanned your career in city planning

[larsenc]

This needs to be run again with TMPE optimized intersections,

[thoraero]

We shall recognize the guy named Jazumojo as one of the craziest junction designers.

[RX_GL]

8-way pinavia interchange: hold my dollars

[Torbmorb]

With lane mathemathics and Hugo many of those intersections would have worked much better and Biffa would be very proud.

[ralphjames]

Holy shit @ 8:16! 😮😮😮
Just the signage leading up to the interchange would be cause for driver confusion!

[complexcitiesskylines]

Biggest help for me is changing the number of lanes so a 4 lane drops to a 3 lane when theres an exit and back to a r lane when the entrance lane comes back on.

[fetzie]

My main take-away from this, is to plan your highway network so that you don't have four of them converging in one location :) There's a fairly good reason why you hardly ever see more than two of them coming together (looking at a map of German Autobahns I'm struggling to find any instance of anything more complicated than a fork or a single cross junction).

[Duckyosis]

8:15 average drive to work in Los Angeles

[kevineusebio]

6:55 the u-turn on the freeway fudged that up

[Xflect]

Although this looks cool, I've never come across a need for an 8 way interchange

[juanjoquispe]

Loved the video. Was surprised by the music change at around 3:00. I'm ready to binge more videos on your channel. Keep it up dude

[petrhajduk]

This was like watching traffic in a 4D world :-)

[xaxoon]

The A.I. in City Skylines is so stupid, there are no crossing systems without creating traffic jams. Unless you're using mods, and even then it's very hard to trade. Unless you build something ridiculous and unrealistic like in Video at 8:16. But then you have no more space for buildings because the whole map is occupied by the rounsabout.The game expects the player to use public transport, then the traffic will be noticeably less.

[chipszed]

something we need to come to terms with is that we can't rely on templates to solve our cities traffic problems, we need to view where and why traffic goes where it does and then provide appropriate infrastructure to accommodate for that

[pontuswendt]

AMAZINGNES!!! Wohoo!!!
Nice presentation again!!!

[foxxinrox]

A big help for every single one of these would be some basic lane mathematics. Each inbound and outbound for the various highways should be expanded to 7 lanes and gradually brought down to 3 or 4 further from the actual interchanges to reduce buildup from immediate merging and exiting.

[watchthe]

The interchanges that maintained thru lanes had a higher flow, one factor to remember. The later 3 solutions even if they did not have thru lanes had a much higher pass through with less standing traffic. I might hve put a trafic circle in the center of them so the lost would have a recovery option. The signage on that mess has to be a headache inducer too. The separate interchange solutions sorting the 8 into 4 and then routing the 4 would probably be the way I would go. Flowing 4000 vehicles seem to be what is needed? so using 4 stack interchanges might be what the doctor ordered with Longhaul express lanes just punching thru without ramps at all.