Cars on Highways

[Falafel MAN]

I am an experienced cities skylines player but i have this problem that every time I built an onramp on an highway all the cars on the highway merge on the left lane. this is causing major backups. Someone knows why this happens? It has nothing to do with me beeing stupid and not knowing how to plan a sufficient city. It just happens with onramps ... Thanks for your help!!

[ancienthighway]

I assume you are useing left hand drive, so the left lane lead to the exit ramps. I also assume that at some point down the road, there is another exit ramp.

There are two ways of handling this in a vanilla game. You do need Mass Transit to get the 2 lane and 4 lane highways. Network Extensions 2 if you don't mind a modded game will give you 5 and 6 lane highways if those would be needed.

https://steamcommunity.com/sharedfiles/filedetails/?id=1468535169
By widening the highway before the ramp, you create a turn lane. Only traffic taking the upcoming ramp will get in that lane. The highway goes back to three lane after the exit.

https://steamcommunity.com/sharedfiles/filedetails/?id=1468535231
Instead of widening the highway before the exit ramp, you could narrow it to two lane after the exit ramp up to the entrance ramp. Again only traffic using the upcoming exit ramp will get into the turn lane.

[OneJasonBradly]

This clip is right hand Highway traffic though it may hold ideas for you.
https://steamcommunity.com/sharedfiles/filedetails/?id=1429565631
There are a few reasons for traffic to force itself into a lane. A screenshot (somewhat wide one) of the area might be helpful to give better advice.

[kristofburger]

Originally posted by ancienthighway:

I assume you are useing left hand drive, so the left lane lead to the exit ramps.

I don't know why you assume that, the OP actually seems to be from a country with right hand drive. In right hand drive, this is probably because of using on ramps with two or more lanes; cars are programmed to clear lanes for oncoming traffic. It's best to use the standard highway ramp if it's merging into the standard three-lane highway.

[ancienthighway]

Originally posted by kristofburger:

... cars are programmed to clear lanes for oncoming traffic.

We apparently have a different understanding of the way traffic in C:S works. In my experience, traffic will get into the lane that leads to it's next turn as soon as it can. Not to clear the lane for other traffic. Driver courtesy was not programmed into the game. There are plenty of examples on you tube and in screenshots of traffic lined up coming into traffic that go as far as the camera can see in both directions, while they other lanes of the highway are empty.

This AI behavior is why all the cars are trying to get into the same lane as soon as they enter the highway. A left turn is ahead that all seem to want to take. The problem the OP has is not with the onramp, but with the off ramps and the traffic queue trying to use them.

You are right about my faulty assumption that the city was set up with left hand drive. There wasn't enough information for that assumption to be made.

[CyberVibes]

He has the issues with onramps but i'm with you on adding an extra lane from 3 to 4 lanes before on and after off ramps, and the longer the lane to on/off ramps the better particualry on busy intersections.

[kristofburger]

Originally posted by ancienthighway:

Originally posted by kristofburger:

... cars are programmed to clear lanes for oncoming traffic.

We apparently have a different understanding of the way traffic in C:S works. In my experience, traffic will get into the lane that leads to it's next turn as soon as it can. Not to clear the lane for other traffic. Driver courtesy was not programmed into the game. There are plenty of examples on you tube and in screenshots of traffic lined up coming into traffic that go as far as the camera can see in both directions, while they other lanes of the highway are empty.

Cars clearing the outside lane for oncoming traffic is a highway specific rule to help high-speed merging, and it's only overridden when traffic towards a certain exit is severely congested. This is easy to observe once you have a non-congested situation, and it's also briefly covered in the Beginner's Guide to Traffic.

[Falafel MAN]

okay. First of all thanks for your tips. I am using 4 lane highway but it doesnt matter how many lanes i have the traffic staying on the highway is always using only one lane (far left lane) and then just few meters before the offramps some cars change to the right lane. but the other lanes are not used. So everytime there is an onramp the cars already on the highway choose the far left lane and leaving the other lanes empty (doent matter if its 3, 4 5 6 lanes hgihway). I tried just banning trucks from the left lanes and now the trucks use one other lane but this cant be a solutionn????

Hope u know what I am meanig by all the things i am saying :)

Thanks

[Sneaky_Koala]

Originally posted by ancienthighway:

I assume you are useing left hand drive, so the left lane lead to the exit ramps. I also assume that at some point down the road, there is another exit ramp.

There are two ways of handling this in a vanilla game. You do need Mass Transit to get the 2 lane and 4 lane highways. Network Extensions 2 if you don't mind a modded game will give you 5 and 6 lane highways if those would be needed.

https://steamcommunity.com/sharedfiles/filedetails/?id=1468535169
By widening the highway before the ramp, you create a turn lane. Only traffic taking the upcoming ramp will get in that lane. The highway goes back to three lane after the exit.

https://steamcommunity.com/sharedfiles/filedetails/?id=1468535231
Instead of widening the highway before the exit ramp, you could narrow it to two lane after the exit ramp up to the entrance ramp. Again only traffic using the upcoming exit ramp will get into the turn lane.

Just my 2 cents but cheers for this.

[mbutton15]

Originally posted by Falafel MAN:

Hope u know what I am meanig by all the things i am saying :)

Thanks

A screenshot (or 2) or, better still, a savegame for people to investigate will allow likely provide a much faster resolution to the issue.

[OneJasonBradly]

Originally posted by Falafel MAN:

okay. First of all thanks for your tips. I am using 4 lane highway but it doesnt matter how many lanes i have the traffic staying on the highway is always using only one lane (far left lane) and then just few meters before the offramps some cars change to the right lane. but the other lanes are not used. So everytime there is an onramp the cars already on the highway choose the far left lane and leaving the other lanes empty (doent matter if its 3, 4 5 6 lanes hgihway). I tried just banning trucks from the left lanes and now the trucks use one other lane but this cant be a solutionn????

Hope u know what I am meanig by all the things i am saying :)

Thanks

This sounds like you are using multi-lane ramps instead of the single ramp lane. In a normal use of a three lane highway (in City Skylines) traffic will move from the right lane to middle lane when approaching an “On ramp” (single lane). Traffic does this to allow the oncoming traffic to do so easily. So on a three lane highway if you use a two lane “On ramp” then the highway traffic will move over two lanes when approaching this On ramp. If you use a three lane highway piece as a connection ramp between two highways this will confuse the traffic and force them to the far left lane because they don’t know which lanes are meant for which highway. Are you using multi-lane for your On and Off ramps? If yes then reset them back to single lane to see if this will correct the issue.

[ancienthighway]

Besides my previous post in using different size highways to help control lane usage, if you do use TM:PE you can use the lane connector tool to control when lane changes occur and how many lanes can be changed at one time.

https://steamcommunity.com/sharedfiles/filedetails/?id=1469167848

[MarkJohnson]

Originally posted by Falafel MAN:

I am an experienced cities skylines player but i have this problem that every time I built an onramp on an highway all the cars on the highway merge on the left lane. this is causing major backups. Someone knows why this happens? It has nothing to do with me beeing stupid and not knowing how to plan a sufficient city. It just happens with onramps ... Thanks for your help!!

Are you connecting the off/on ramps to the segments of the highway (the round circles?) If not, it will make small segments and give you short pieces of road for them to switch lanes and can cause backups. Maybe try bulldozing the highways two or three segments from the on/off ramps back. Then lay the highway again from the on/off ramp back to the highway, so there is a long full segment of road for lane switching.

Maybe add more on/off ramps along the highway for more entry/exit points.

Make sure why they are all going to this area. Check where they are com ing from and going to with the route tool.

If it's mostly freight traffic check you exports. you don't gain anything extra by exporting and can eliminate the excess freight to clear up roads.

If it's a new construction area, then it will just be busy until you finish building and after the area matures.

But everyone in the left lane is normal. It gets traffic out of the way for merging traffic. This way traffic can switch lanes without running into other cars.

[A Fat, Angry Serval]

You know, it still, to this day, baffles me that people never simply suggest that you give every lane somewhere to go. Traffic AI in Cities Skylines works in a very specific way that makes having extra lanes useless without giving the game a reason to use them:

1. A vehicle will determine the route it needs to take at the start of a trip.
2. The routing AI ignores traffic density and flow.
3. While traveling, a vehicle will change to the lane it needs to be in as soon as possible every time it makes a turn, regardless of existing traffic. However, it will slow down or stop to avoid other vehicles.
4. As a result, if you have a six-lane one-way road but only left-hand exits off the road, traffic will insist on using the far left lane ONLY.

Thus, the best way to use wider roads is give traffic a reason to use every lane. Which means that roads should widen as traffic merges on and narrow as it merges off. Here's an example of the latter:
https://steamcommunity.com/sharedfiles/filedetails/?id=1469294201
With this setup, traffic will use the left two lanes of the 6-lane one-way to turn left at the first intersection, the middle two lanes to pass through the first intersection and turn left at the second from the left two lanes of the 4-lane one-way road, and the right two lanes to go straight.

[Saber Kitsune]

Originally posted by ancienthighway:

<snip>
https://steamcommunity.com/sharedfiles/filedetails/?id=1468535169
By widening the highway before the ramp, you create a turn lane. Only traffic taking the upcoming ramp will get in that lane. The highway goes back to three lane after the exit.

https://steamcommunity.com/sharedfiles/filedetails/?id=1468535231
Instead of widening the highway before the exit ramp, you could narrow it to two lane after the exit ramp up to the entrance ramp. Again only traffic using the upcoming exit ramp will get into the turn lane.

I get the idea behind this, but it doesn't work exactly how you think it'd work in game. First reason being is that when a roadway gets a new lane added to it, it gets added to the left side (assuming they drive on the right side of the road) 4-lane highway into 6-lane one way is the only exception (that I know of) and even then it still follows that rule to a degree as lanes #1 and #3(left lanes if you split the 4-lane down the middle) split into the new lanes.

Secondly, any highway grade segment that "merges" onto any other segment, street or highway, they turn onto the closest lane they can. This is the part of what kristofburger was refering to earlier. They do this even if they should be able to turn onto the next closest lane. This means multi-lane onramps won't work as expected either.

Examples: https://imgur.com/a/p1bsV6L
First image: a 2-lane road turning onto a 4-lane highway
Second: 2-lane highway turning onto a 4-lane highway
Third: single lane highway ramp onto 4-lane highway

As you can see the highway grade pieces cause traffic to change lanes after joining the highway, even it would've been possible to get into their desired lane to begin with. Make sense when you think about it. You merge one lane at a time instead of just divebombing across lanes.

In addition, highways already have dedicated exit lanes programmed in, even if the lane markings say they can go straight. ( Given that it can be assumed that players will mimic real life and keep offramps on the same side, and also given that Cims pick lanes early, if it wasn't programmed like this the left lanes of highways would receive little, if any, traffic. All the traffic would be concentrated in the rightmost lane which gives access to offramps. This "lane fuzzing" is the second part of what kristofburger was talking about.

This lane fuzzing results in more traffic using the left lanes, even if there are no offramps on the left side. Which of the left lanes used is roughly dependent on how many exits are between where traffic gets on and where they want to get off. Generally more exits between extry and exit means it's more likely they'll use the far left; less exits mean more towards middle lane.

Taking all this into account, it means that while your suggestion isn't bad, it can create a few traffic issues down the line.

Here's why: https://imgur.com/a/IAOS17W

Top image is essentially what you've suggested. Left input lane ends up splitting into both the left and middle lanes of the output. Middle input ends up being the right lane of output, and the right lane of input exits. So you effectively only have 2 dedicated through lanes despite having a 4 lane section, due to this lane shifting effect. Put several of these in a row and you basically only get 1 through lane overall, as the other lanes will eventually turn into exit lanes. Good for if you want to draw traffic into the left lane, bad if you want to draw traffic away from the left. However, unless you're dealing with an insane amount of traffic, this shouldn't hurt that badly. Still, this design makes traffic control harder, and can cause traffic jams nowhere near it.
Bottom image is functionally what you want. All 3 lanes retain their status as they go through. Left lane splits onto the exit lane, while the onramp stays its own dedicated lane. OneJasonBradly's video has some variants of this format.

TL;DR: The leftmost lane, not rightmost, splits into extra lanes on a roadway, and traffic tends to pile up in the left lane as they drive along a highway.



Anyways, back to the topic. Falafel MAN, I assume your issue is something like this?: https://imgur.com/a/YEgxdAF
If so, my suggestion would be combining offramps to reduce the total number of exits, as well as helping to reduce weaving due to the extra space between exits. Basically try for a variant of a local/express lane setup, like this: https://imgur.com/a/oUW5Vy2
Multi-lane exits are also a possibility, but builder beware as they can cause more traffic if lane shifting isn't properly taken into account.

(Yeah, after that wall of text my advice to OP is to make less offramps. ¯\_(ツ)_/¯ Someone's gotta find this info useful at least.)

[OneJasonBradly]

Originally posted by VestedGamr:

You know, it still, to this day, baffles me that people never simply suggest that you give every lane somewhere to go. Traffic AI in Cities Skylines works in a very specific way that makes having extra lanes useless without giving the game a reason to use them:

1. A vehicle will determine the route it needs to take at the start of a trip.
2. The routing AI ignores traffic density and flow.
3. While traveling, a vehicle will change to the lane it needs to be in as soon as possible every time it makes a turn, regardless of existing traffic. However, it will slow down or stop to avoid other vehicles.
4. As a result, if you have a six-lane one-way road but only left-hand exits off the road, traffic will insist on using the far left lane ONLY.

Thus, the best way to use wider roads is give traffic a reason to use every lane. Which means that roads should widen as traffic merges on and narrow as it merges off. Here's an example of the latter:
https://steamcommunity.com/sharedfiles/filedetails/?id=1469294201
With this setup, traffic will use the left two lanes of the 6-lane one-way to turn left at the first intersection, the middle two lanes to pass through the first intersection and turn left at the second from the left two lanes of the 4-lane one-way road, and the right two lanes to go straight.

A clip that enforces what is said here.
https://steamcommunity.com/sharedfiles/filedetails/?id=1308740009