EDIT: why do all cars prefer 1 lane?

[Squirting Elephant]

http://steamcommunity.com/sharedfiles/filedetails/?id=1179821080

Why do they still all prefer that one single lane on that road? Even the vehicles that just need a left turn and then remain on the straight part also want that one specific lane even though there are 2 lanes now for it.

Same here and on several other spots:
https://i.imgur.com/2bKD0b9.jpg

This is what is causing my jams everywhere (depending on time of day) for this crossing. There is no guide, no Reddit and no Steam post that I could find that explains this into detail.

What's so weird is that vehicles that need to go left want the same lane as vehicles that want to go right. Makes no sense (EDIT this seems to be a bug).
I connected the 4th lane on that side but again, no difference. They all swear to that one lane :/

Update

So I have a whole list of partial solutions and I know what the most important solution is (now). But I still would have to work out the exception-cases and work out how to go from 4 lanes to 6 lanes and how highway ramps fit into this and etc. etc. etc. Pfff... And after that I would have to start my city all over from scratch again to fit these new designs.

I'm sorry... This is too much work. I just want to play and build a city instead of having to work/research & hack my way around this. On top of that there is a possible bug that halves the lane-usage.

What we got so far:

Suggested solutions that I could not verify to fix anything:
1. Use TMPE (this mod does not work for me personally).
2. Use more intersections.
3. Have longer roads between intersections (screenshot proved this does not work). You can make infinitely long roads and they will all use one lane from the very start.
4. Some road designs from the guides (Which are supposeod to be perfect) also are effected by this problem. Most likely caused by most cims from the same source area going to the same destination area.
5. Use alternative roads to the destinations (all those cims that come roughly from the same source and whom go to the same destination will ignore these alternative routes).
6. Use smaller roads with less lanes because they don't use all lanes anyway. True this is more efficient if not used anyway but this is not a/the solution.


Solutions that I can verify work at least partially for some use-cases:
1. Use less intersections and less overly convoluted interchanges with multi-lane ramps.
2. Use more one-ways (works wonders if implemented right but it can be ugly/a pain).
3. Use exits on both left and right sides instead of on one side.
4. Split destinations for cims that come from the same source area as much as possible (so far, by a lot, this is the biggest impact-solution).
5. Use roads without intersections from source to destination. Works sometimes but is not exactly design (huge wastes of space and you will need enormous amounts of roads)
6. Have housing&commercial with a freeway in the middle and exits and entrances on both sides of the freeway (this works because this is how I did my previous city but it forces you into a specific design. Therefor I can at most say this is a partial solution).


Notes:
1. There is (at least for me, not sure if caused by a mod) a bug that causes vehicles to use 1 (invalid) lane instead of 2: https://i.imgur.com/eJGYAxv.jpg

Another update with useful posts:

Originally posted by Stealthy:

Key issue is to understand that traffic works like GPS. Route is calculated with lane selections and turns when the car is spawned and is not changed at any point, unless player changes the road layout. Hence, cars always prefer to take lanes as early as possible.

Highways: Cars want to avoid the slip road / off ramp and only traffic leaving the highway will use the lane closest to the ramp. If you use left and right side ramps, you effectively squeeze traffic going past both ramps to middle lane.

Off-ramps: If you got 2 or more lanes in them, cars will take the lane which leads them closest to the side of the road where they need to be at the next turn, turn after that and so on. So even if you got 2 lanes turning left, but car will turn right after making that left turn first, it will use right hand lane, never left hand lane.

Normal roads: 6-lane roads are extremely rarely needed in this game, and only as a main route. Never use them more than necessary. 4-lane roads will cater most of your bigger roads, majority of roads using small roads, be it one way or normal 2-way streets.

To get cars using all 3 lanes per direction on 6-lane 2-way street, you need to provide turns to left and right, and possibility to go straight. And then of course, reasons for cars to make those turns.
On 6-lane one way road, same principle applies. You need 2 lanes to left, 2 lanes straight and 2 lanes to right. But even if you got these, and there is only one direction after those turns to left or right, cars will use only one lane, the one leading closest to the turn / correct side of the road.

Spacing of the junctions on any road type is critical as cars only change lanes on node points. If 2 junctions are so close together, that there is no nodes between (blue circle on road tool), then cars will not be able to change lanes on that stretch of roads and this will affect their lane selection. This is why sometimes your bus can't make the turn you wanted it to take, stop is too close to the turn, and there is no node point for it to use for lane changing.

Length of the section between junctions also determines the capacity of that junction. Cars will not drive into blocked junction when going straight, so there must be space for them at the other side of the junction. If the section after junction is short, maybe 2 car lengths, then only one or 2 cars at a time can pass through and rest will have to wait until these 2 cars vacate the section after the junction.

Originally posted by SkiRich:

Even with multi lane roads available and lanes clear, if a truck or hearse is tending to a commercial property, that lane is effectively blocked, and all traffic that decided to use that lane will wait till the truck or hearse will leave. They will not take the effort to go around unless you use a Traffic Manager Mod.

That said, to effectively prevent this, especially on those assets that have conga line of trucks coming and going, make a one way small road just off the main road you wanted, connected at both ends just before and beyond the asset back to the primary road and put that asset on that road. You in effect create a load/unload road for the asset allowing other traffic to bypass the high traffic asset.

Originally posted by Squirting Elephant:

<modified>I made some test cases. A red line is my estimated lane usage and I assume the big center road to be infinitely long. Also I assume here that traffic wants to visit each exit more or less equally (because otherwise roads would 'break' anyway):

Case 1:
https://i.imgur.com/7ETk8Px.jpg
I assume that 5 lanes will be used? Wait I got it wrong. Only 3 lanes would be used. Here is a corrected version that I believe will use 4 lanes (leaving 1 center lane and 1 left-lane unused): https://i.imgur.com/PxkONxa.jpg

Case 2:
https://i.imgur.com/3v9uRvX.jpg
I assume that 4 lanes will be used? Also wrong, same as case 1. Only 2 lanes will be used. This is how it would work (only 3 lanes): https://i.imgur.com/8QGzkWy.jpg

But how do I force usage of the center 2 lanes? I mean I can have 2 or more left-exits, 2 or more right-exits, but I can never have more than 1 'exit' going straight. The moment I add a second one it will just see it as left&right instead. So how can I force-use the second center lane?

Case 3 (4-lane-highway):
https://i.imgur.com/MmFzcf9.jpg
So because there are no secondary exits after those exits, it will use only 3 lanes rights?

Case 3a:
https://i.imgur.com/wiAfxvz.jpg
Why is this case bad (no off-ramps but highways instead)? I know that only 1, at most 2 lanes are gonne be used.
Answer: You shouldn't use highways because a) you don't need them on ramps and b) they will not be fully used anyway and just cause havoc on AI due to fact that straight going traffic tries to avoid outside lanes near ramps. If you got 3 lanes turning off, it means 3 lanes are not used by straight going traffic.

Case 4:
https://i.imgur.com/v06Xb8k.jpg
Will this cause 2 lanes to be used instead of 1 for going left? This might work if you use 2 lane highway first, then split it into 2 one lane going separate directions.

Case 4a:
https://i.imgur.com/8lK61lk.jpg
Probably only outside lane is used for both exits, since they start from same node.

[Squirting Elephant]

I tested this with another highway and there they also used 1 lane. Cars started doing this 3 or 4 roads ahead of it. Even across multiple road types (like regular roads, bridges, then highways) and supplying multiple ways to the destination doesn't help they all stick to 1 lane on ALL of those roads. Supplying left and right splits doesn't help... Huh... Looks like a bug.

Google didn't help me either. Tips like

Build more entrances to that specific area. Make all of the entrances flow better so there are no stoppages. Don't use roundabouts. Have longer roads before intersections. Interchanges to close together, having exits and entrances from the fast lanes, having too many.

Do not apply for my case. Well maybe "having too many" but this looks like a bug to me if that's the case.
I also tried replacing highway-exits with ramps like described in the traffic guide but that did not help either:
http://steamcommunity.com/sharedfiles/filedetails/?id=522776740
Besides ramps are bad. They are only a single lane. Even if it would work, merging 2 to 4 lanes into a single lane (and 80km/h instead of 100) will obviously cause other problems.

The only solution I found so far was:
http://steamcommunity.com/sharedfiles/filedetails/?id=583429740&searchtext=traffic+manager
But really I have to use a mod... I expected the Mass Transit DLC to include this stuff.
However using this mod I noticed it bugged out straight away. Cars that are on lanes that are only allowed to go right suddenly go left... After forwarding time I noticed that this mod somoetimes mirrors the lanes (=bug) and worse. So that is no option either:
https://i.imgur.com/TXtxgOD.jpg
Could be a mod conflict or the mod itself is buggy but either way... There is no build-in feature in the game to prevent this 1-lane-nonsense?


I'm kinda clueless now.

[Squirting Elephant]

Another example:
https://i.imgur.com/IiySFM0.jpg
Yes this connects to that turbine-crossing, it goes really far back across multiple roadtypes and whatnot. It starts in the suburban area where they leave they leave from their home. So start --> finish, 1 lane...

Apparently the cims are like: "hey I just left my driveway, I'm still inside the suburban area, I need to turn right in about '1000km' from now after 3 highways and etc, so let's go to that lane already".

You can see that the crossings are not too close together, using ramps also fails. Maybe 3 or 4 cars use another lane (yay...). I used everything I could find on Google and on the guides. I give up...

[Diviance]

It is just the way the pathfinding works in the game so that lower-end machines can play too. The route the car takes is determined when it spawns and doesn't change unless the route is no longer available. It chooses the "fastest" route and doesn't take traffic into account. So they end up bunching up in one lane, depending upon how you designed your roads. There are tricks to take advantage of the pathfinding, though.

[SkiRich]

Originally posted by Diviance:

It is just the way the pathfinding works in the game so that lower-end machines can play too. The route the car takes is determined when it spawns and doesn't change unless the route is no longer available. It chooses the "fastest" route and doesn't take traffic into account. So they end up bunching up in one lane, depending upon how you designed your roads. There are tricks to take advantage of the pathfinding, though.

this is accurate. this is how the deveopers coded the AI to reduce CPU calculations.
The only way to change this is to apply another traffic AI that corrects this.
TMPE has logic to change this at a cost to cpu performance.

[kristofburger]

All you should ever need from that mess is the turbine interchange core, and the ramps don't need to be three lanes. Everything else in that first screenshot is completely redundant as far as highways go.

The base reason for them sticking to one lane is because they want to avoid blocking other directions in heavy traffic (all cars drive the same speed = no overtaking). Building overly convoluted interchanges with multi-lane ramps tends to confuse this behavior, which is why you should avoid unnecessary spaghetti.

Originally posted by Diviance:

It chooses the "fastest" route and doesn't take traffic into account.

Then again, if they didn't take other traffic into account the cars wouldn't be in one lane that much. They don't pick another road, but it's more organized than it may seem.

[SkiRich]

Originally posted by ristosal:

All you should ever need from that mess is the turbine interchange core, and the ramps don't need to be three lanes. Everything else in that first screenshot is completely redundant as far as highways go.

The base reason for them sticking to one lane is because they want to avoid blocking other directions in heavy traffic (all cars drive the same speed = no overtaking). Building overly convoluted interchanges with multi-lane ramps tends to confuse this behavior, which is why you should avoid unnecessary spaghetti.

Originally posted by Diviance:

It chooses the "fastest" route and doesn't take traffic into account.

Then again, if they didn't take other traffic into account the cars wouldn't be in one lane that much. They don't pick another road, but it's more organized than it may seem.

Actually all cars do not drive the same speed. I have seen overtaking, but in the default no mod condition everyone is on one lane.
When you add something like TMPE you can actually see cars wizing past trucks and you can tell trucks to move over to the slow lane.

[Squirting Elephant]

Originally posted by Diviance:

It chooses the "fastest" route and doesn't take traffic into account

Yeah I feared this already. When trying to solve this 1-lane-nonsense I noticed this by accident. Not always the case though but mostly yes.

So I have 4 lanes but ~95% of the cars need to drive to the same area and thus they all take the same lane. But... What is the whole use of those 4 lanes then if the game can not use more than 3 (left, straigh, right)?
It get's worse when I noticed that I have a lane with a right arrow and a line with a straight+right arrow, the cars still refuse to use 2 lanes and go with 1 lane instead even though 2 lanes bring them to their destination. This looks buggy. The devs could at least have added a 50% RNG element (costs no performance) so that cims take at least 2 lanes in this particular case.

I tested some more and gave cars 2 lanes from start to destination (same road), yet they still take only 1 lane like 98% of the time. Sorry but this is completely stupid!

Originally posted by SkiRich:

TMPE has logic to change this at a cost to cpu performance.

TMPE has serious bugs for me. Could be a mod conflict (but none of the ones it listed as incompatible) but I kinda need my other mods so TMPE is not really a solution.

Originally posted by ristosal:

The base reason for them sticking to one lane is because they want to avoid blocking other directions in heavy traffic

In this case this mechanic is sadly doing the opposite. It blocks 2-3 lanes just to get to 1 lane.


I could solve this by changing my entire city-layout including rezoning just about everything (not feeling like it).

I could remove some of the spaghetti and use a 2-road-turbine instead of a 4-road-one and use ramps but this is not enough throughput (I can actually fill up an entire highway with traffic even when they do not use 1 lane). For some reason my cims refuse to use the (free) mass-transit and prefer to drive.

I think that the devs could give us an ingame option to disable this nonsense at the cost of more performance drain. Because now it seems that a alot of completely sane and logical designs do not work.

[kristofburger]

Originally posted by SkiRich:

Actually all cars do not drive the same speed. I have seen overtaking, but in the default no mod condition everyone is on one lane.

Only differences in speed occur when a car gets a flying start from a stoplight, and emergency vehicles. Top speeds are always the same on a given road.

[Squirting Elephant]

I found an actual bug (is the part right after they went onto 1 lane, the problematic part): https://i.imgur.com/eJGYAxv.jpg

I had this same problem with TMPE but it seems I have it even without that mod. So this particular bug is not TMPE.

So they should not even be allowed to go onto this one lane... It's a bug.

Another screenshot (omg a red car actually used the 2nd lane here for once):
https://i.imgur.com/BuURod7.jpg
I never noticed this before for this road (at which I have been looking for hours now) but they are virtually all taking the wrong lane for turning right. Is this another "performance feature"?

[kristofburger]

Originally posted by Squirting Elephant:

Originally posted by ristosal:

The base reason for them sticking to one lane is because they want to avoid blocking other directions in heavy traffic

In this case this mechanic is sadly doing the opposite. It blocks 2-3 lanes just to get to 1 lane.

There's a small but potentially decisive fix to this, regarding the intersection immediately after this pile-up. Try moving that to split off of the ramp that takes traffic northbound

[Squirting Elephant]

I put the exit on the left side instead of on the right side. Traffic now actually uses 2 lanes instead of 1 and sometimes even 3. But on the next exit it goes back to 1 lane, thus bottlenecking everything again.

Also highway-ramps have an extremely high chancec of forcing all traffic onto one lane (because this is only 1 lane).

And then I noticed another problem (got this part straight from the traffic guide so it should be perfect but it is not once population reaches 100k):
https://i.imgur.com/QhIzjjn.jpg
This comes somewhere after the turbine.

So 6 lanes go right into another 6 lanes. Traffic splits up (about equally) into 3 left and 3 right. So if there are 6 lanes, 3 going left, 3 going right, with no other options at all, why the heck do they use only 1 lane? Is this again for performance reasons?
Even for the splitting it uses only 2 lanes (1 left, 1 right) instead of 6. So again basically 1 lane again. This is infuriating and I'm like 99% sure that the wrong-lane-thing is a bug (maybe the 25 tile mod caused it?).

BUT, the other entrance (topleft) is working perfectly with 5 out of 6 lanes in use. Oh man. I'm sure there are ways to have the AI use all 6 lanes as we can see but it requires really odd and weird specific cases.

Even using only one-way-roads as we can see can cause this. Even a one-way-road with a T-junction is too stupid to use more than 1 lane. I mean... Nevermind... Basically tons of valid road designs won't work anymore for big cities because of "performance reasons" (and at least 1 bug) and no option ingame to change this other than TMPE (which bugs for me) so basically I can quit the game after about 50k pop because there are only a handful of valid designs left to use. No fun... I want to design my own... If I want spagetti I should be able to. But no :(

[rovaira2]

What I try to do is is have housing with a freeway in the middle.. I also try and do that with commercial when possible. I'd have exits and entrances on both sides of the freeway. This divides traffic up better.

I don't always design them this way at first, but it does help.

Also I have on and off ramps on both sides of the freeway; for example an exit on the right, then the left, etc.

If building a 3 lane road for example I'd try to have a road at the end going straight, one going right, and one going left. That way cims seem to use more lanes.

[Super Earth Ceremonial Guard]

"why do all cars prefer 1 lane?"

Because you built your city in a way where they all want to take the same turn.

Split your areas and plan your roads better. They'll only use the other lane(s) if they are heading further down the road to the next turn(s)

[SkiRich]

Without adding a Trafiic AI mod you are stuck doing one of three things to fix this.
1. Be creative in road design, using one way roads and more intersections.
2. Spread your city into zones on different sides of the street/intersection.
3. Deal with the one lane issue and plan the city around that.

I already told CO I wont play the game if I cant get a traffic manger AI to run and they wont make a smarter AI. That's my personal preference. You have options though they are limited.

[OneJasonBradly]

There is nothing wrong with the AI agents. There is something about the traffic mechanics you are taking for granted. Limit the build to 30k or 50k till you experiment more with the traffic and road and intersection building and understand how it works. You can certainly build spaghetti roads all you want as long some common rules.
http://steamcommunity.com/sharedfiles/filedetails/?id=864930921
http://steamcommunity.com/sharedfiles/filedetails/?id=925376898
http://steamcommunity.com/sharedfiles/filedetails/?id=810771996
http://steamcommunity.com/sharedfiles/filedetails/?id=776084563
I personally don't use Traffic Manager so I know this can be achieved without it.