DDI= Traffic Nightmare! Please help!

[scpool1986]

This interchange serves a predominantly industrial area that is also home to about 80% of my disaster response units, a trade school of around 800 students, and an Ultimate Recycling Center. It was working out great until the industrial area finished filling in and now the traffic is backing up until the waterway, this is on the in game vanilla ‘islands’ map on the large island just off the mainland. I tried simply upgrading to more lanes which just multiplied the problem. Any suggestions on what to do next or a more appropriate interchange for this area?

https://steamcommunity.com/sharedfiles/filedetails/?id=1760092779

[OneJasonBradly]

Yes, that first street I think need to change access to that street via to the north rather than that close to the highway interchange. The second issue is the traffic coming into the area from the overpass is in the right lane rather the left and I believe that first street is causing that issue. Because they are in the other lane and there is no room to change lanes after exiting the interchange structure. Traffic will collide at that spot where the two inputs to the area meet.

[TLHeart]

Merge point is the first conflict... I assume no mods to control traffic lanes. Second conflict is at the bottom of the bridge where you added the 6 lane road. That causes another intersection as far as the game is concerned, so the traffic stops, at the bottom of the bridge until the lane on the other side is clear.... and then you have another intersection a very short distance away. Which again causes the cars to pause to make sure the path is clear. So you have a large area of no traffic, as each vehicle waits.... and backs up...

to fix without mods, upgrade the bridge from the diverging diamond to your six lane road. reduces the number of intersections, and pauses. Allows traffic to pick their lanes at the merge.

with mods, I would use Traffic manager presidents addition to control the lanes at the merge, and remove the intersection restrictions so the traffic can flow through those dead spaces.

[ebrumby]

Diverging diamond interchanges never work well for me. There are some good YouTubes that rate various interchanges on the web and may help you pick a better one such as this one: https://www.youtube.com/watch?v=yITr127KZtQ.

[ams083]

Change out that interchange.

[OneJasonBradly]

Originally posted by ams083:

Change out that interchange.

agree

[TLHeart]

a diverging diamond interchange that is built correctly, which that one in his city is not, work well. The merge points are messed up.

Biggest problem is the changes of roads and intersection all cause the vehicles to pause at each change, to check that their lane is clear...

[scpool1986]

I used some of your suggestions and while it did stop vehicles from stopping before going on to the 6 lane road and relocated the access road for my disaster response service and fire fighting helicopter depots to the stretch of 6 lane road that goes to the trade school but it only put a little dent in the backup.
https://steamcommunity.com/sharedfiles/filedetails/?id=1760349455

Originally posted by tenderloveheart:

a diverging diamond interchange that is built correctly, which that one in his city is not, work well. The merge points are messed up.

Biggest problem is the changes of roads and intersection all cause the vehicles to pause at each change, to check that their lane is clear...

I didn’t build it, I downloaded it from the workshop. What are some design changes you’d recommend. The backups are now going into the main area of the city.

[Markus Reese]

Seriously? You need my square-a-bout or do a double herringbone off the highway. I dont have the herringbones shared, but you can see it in my thread about inferior roundabouts.

Take a peek at the way I do high flow.

https://steamcommunity.com/sharedfiles/filedetails/?id=1750797813

One off, one for on. Keep it in a big circle essentially. You can make it a loop by having a third middle exit between the two where they merge to cycle around. Is late else would sketch it up.

[TLHeart]

looking at your last screenshot, part of the problem is the way the vehicle pathfinding handles highway exits... causing the traffic to merge and cause backups just before the exit... upgrade the highway to a 4 lane before the exit to cause a turn/exit land, or downgrade to 2 lanes just after the exit, which also will create the exit/turn lane. That way traffic going straight on the highway are not waiting for the exit traffic to clear.

Without mods it gets complicated to get the traffic to use both lanes at the merge points. The pathfinding does not do good with choices at intersections, between straight or turn from the same lane. We have to force that decision for them.

Hard to tell, but it looks like on the cross at the industry side has been changed to 1 lane, while you are trying to handle 2 lanes of traffic, causing a bottle neck.

Rule in skyline, one lane plus one lane merging in requires 2 lanes after the merge, for heavy traffic. And 3 lanes are rarely needed, except to create a turn lane.

It also appears that You have a 6 lane street into a 6 lane street... causing two lanes to have double choices, which causes the pathfinding to NOT use those lanes, and only use one lane of 3. I would downgrade that cross 6 lane street to a 4 or even a 2 lane, since there is very little traffic using it. That would help the pathfinding all the way back to the highway.

Much else I can't really say without seeing the entire traffic.

Are you forcing all industry traffic to enter at exit at that one point? where you have the DDI?

[Pops]

DDI's arent the best, try a dcmi instead or if u have the space a 4 stack interchange. DD!'s can only handle med traffic flow at best.

[Fangorn]

I would personally swap out the interchange. The DDI doesn't seem like it's able to handle the volume. The merges tend to slow things down as well as the crossovers (Through granted it does perform slightly better than a traditional diamond). I personally like the stack or, if you have the room, the turbine (mainly for appearance).
Turbine Interchange: https://steamcommunity.com/sharedfiles/filedetails/?id=1760649857
Stack Interchange: https://steamcommunity.com/sharedfiles/filedetails/?id=1760668262

[Randox]

How much traffic are you planning on ultimately? If there is going to be a lot of traffic going both ways, you need a proper interchange. Or if sanity is taking a backseat to compactness, a gothic cross.

If most of the traffic is going to be the existing roads though, I'd just tear that interchange out and replace it with a trumpet a bit further down and run a 2 lane highway back to the road, and replace the bridge with a 4 lane road.

[scpool1986]

Originally posted by twistedmelon:

Seriously? You need my square-a-bout or do a double herringbone off the highway. I dont have the herringbones shared, but you can see it in my thread about inferior roundabouts.

Take a peek at the way I do high flow.

https://steamcommunity.com/sharedfiles/filedetails/?id=1750797813

One off, one for on. Keep it in a big circle essentially. You can make it a loop by having a third middle exit between the two where they merge to cycle around. Is late else would sketch it up.

To be honest when taking the space restraints into consideration the interchange you posted the picture of probably wouldn’t fit. Here’s a screen shot of the area I’m working with from a different angle.

https://steamcommunity.com/sharedfiles/filedetails/?id=1750399915

Originally posted by Pops:

DDI's arent the best, try a dcmi instead or if u have the space a 4 stack interchange. DD!'s can only handle med traffic flow at best.

I’ve been thinking of a compact DCMI and letting it go for a while to see how traffic goes.

[Markus Reese]

It can. With lower traffic volume, you can come off at 90s plus those are shallow ramps. Will do a quickie draw up tonight when back home. That picture is more of a concept. Note how one side all four roads are exiting and other side is all merging on? The opposed exits spreads out and keeps traffic clear of thru traffic.

Yup, I can definitely get you a quickdrop asset but not for a bit of a while.

Edit: Following is a compact T intersection that worked well. Naturally wouldnt be six lanes. Put one in your main road before the underpass, and do one off the highway would flow very well. Pic is an old screenshot from an experiment.

https://steamcommunity.com/sharedfiles/filedetails/?id=1558707292

[Jarl Ballin]

For everyone saying DDIs aren't effective:

https://www.reddit.com/r/CitiesSkylines/comments/bpuqxc/new_dlc_is_coming_so_heres_me_with_8_large/

It's all about setting it up properly.