Tourists are acting strangely

[Catratio]

I see something strange going on in my city and I don't know how to correct it, if I can.

https://i.imgur.com/PIaL3PJ.jpg

The traffic enters the city limits (red lines), exits the highway at the first off ramp, finds the first intersection they can, immediately turns around and leaves the city the same way they came (blue lines). I had to make that little roundabout because they were going all the way into town to turn around on and clog my dead end streets. I watch this happen and it is ALL "tourists" in their motorhomes and RVs.

I never had this happen before. Maybe because it is a workshop map that uses the two lane highway instead of the normal freeways in either direction? That's really the only thing that's different. I had to build a similar roundabout on the other side of the map too because they were coming into town and either doing non-stop U-turns on the off/on-ramps or going all the way around the block once they got into town just to exit again. I don't understand this behavior.

[AnarchistMetalhead]

just feed them through some automated toll booths ;)
but yes, that is odd behaviour, never seen that before
getting from one edge connection to another is normal traffic, how far apart are the incoming and outgoing roads at the edge?
could it be that they are on opposite sides of a tile divide?

[Catratio]

Exits are 5 tiles apart, at completely opposite ends. I'm using Aquila Sol's Silverwind Valley map. You can see the intial highway layout in the white line:

https://steamuserimages-a.akamaihd.net/ugc/924802734825461916/2C56CD27ACF4E76103920FB026641BFD8D5BE608/

I thought maybe since they are trying to reach the other end they figure it's quicker to just U-turn, but this started at the original intersection in the middle of the map and I never saw this behavior when the map had the one way freeways that spanned the map. But seriously it is JUST tourists. I click their RV and it says "tourist - leaving the city". I only have a population of 13,000 so it's a pretty small town, maybe there's no reason for them to really want to stay in town yet? But why even spawn them in that case? I don't have any mods that affect AI so I don't know what to do here.

[leftbehind]

Dummy traffic. They're not real tourists - it's just random traffic that enters and then seeks an exit to make the highways look busy.

There are some mods that allow you to control the dummy traffic in the workshop.

[OneJasonBradly]

Dummy traffic yes, but to U turn and leave the way they came? No there is something wrong here. Have you tried the " --noWorkshop " launch option to make sure it's not your collection having their way with your map?
Edit; So just the one highway? I think if that highway was broken somewhere then it would do that exact thing, U turn when the can instead of de-spawn when they arrive at the break.

[leftbehind]

No, they always act that way. It depends on the layout of road network. Remember on normal game, the first highway junctions are near the center of the map where your city is - so they can drive in to your city and do a short wander around - because that's literally the shortest route for them to get an exit via any of the outside connections.

Now introduce 81 tiles mod and a highway junction near the edge of the map. What do you think they will do? They are instructed to enter and then leave via random exit, they don't have to drive far do they?

We are looking in to possible features in Traffic Manager to try and prevent such things, but low priority as it really only affects users of 81 tiles when they have junctions near the map edge.

Note that the issue of dummy traffic leaving by same way it came in exists all the time in every game, but if your highway junctions are near center of the map you just don't notice it as much. The closer a junction is to the edge of the map, the more obvious it becomes to the player what the dummy traffic is doing. The more outside connections there are, the more entry and exit points there will be (more randomisation). So another thing that exacerbates it is having very few outside connections. Also, in late game, there is less dummy traffic (due to traffic limit being dedicated more towards tourists and residents etc.) - so it's usually small cities or early game when people notice the issue the most.

[OneJasonBradly]

Though it is the first test I can not reproduce what you state! On a map I start I can not cause any... any traffic to U-turn back out of town. No matter where I place the U-turn road. It would seem not so random. Their choice of destination when spawned is not to U-turn. it is to another exit off the map. so far never the way they came. But will look further to see if there is something to what you state.

Originally posted by aubergine18:

No, they always act that way. It depends on the layout of road network. Remember on normal game, the first highway junctions are near the center of the map where your city is - so they can drive in to your city and do a short wander around - because that's literally the shortest route for them to get an exit via any of the outside connections.

Now introduce 81 tiles mod and a highway junction near the edge of the map. What do you think they will do? They are instructed to enter and then leave via random exit, they don't have to drive far do they?

We are looking in to possible features in Traffic Manager to try and prevent such things, but low priority as it really only affects users of 81 tiles when they have junctions near the map edge.

Note that the issue of dummy traffic leaving by same way it came in exists all the time in every game, but if your highway junctions are near center of the map you just don't notice it as much. The closer a junction is to the edge of the map, the more obvious it becomes to the player what the dummy traffic is doing. The more outside connections there are, the more entry and exit points there will be (more randomisation). So another thing that exacerbates it is having very few outside connections. Also, in late game, there is less dummy traffic (due to traffic limit being dedicated more towards tourists and residents etc.) - so it's usually small cities or early game when people notice the issue the most.

[Meesmoth]

I play a lot on 81-tile maps, plus I have roads near the edge (as I recreate real-world cities), and I gotta say that I agree with aubergine, dummy traffic looks weird when having stuff not possible in base game.

One example is that when I create a national road from west to east, and another one near the edge, all dummy traffic are on the map edge, while the road inside the center tile is empty.

[leftbehind]

@OneJasonBradly : Doing qualitative testing is one thing, actually looking at the source code that spawns vehicles is quite another. And that's what's been done on several occasions when looking in to these sorts of issues in TM:PE, some examples:

https://github.com/VictorPhilipp/Cities-Skylines-Traffic-Manager-President-Edition/issues/175

https://github.com/krzychu124/Cities-Skylines-Traffic-Manager-President-Edition/pull/100

In summary: Game chooses random entrance point, and random exit point. It doesn't check if they are the same (remember vanilla highways are separate road in each direction). It then pathfinds the vehicle between entry and exit via shortest route (pathfinder automatically adds in some randomisation). Fewer entry/exit nodes mean less random routes for dummy traffic. Highway junctions near edge of map make the shortcomings of dummy traffic system much more obvious to users.

If you download ILSpy you can view the vanilla code for yourself (the outside connections classes, dummy traffic, pathfinder, etc).

[AnarchistMetalhead]

Originally posted by Catratio:

Exits are 5 tiles apart, at completely opposite ends. I'm using Aquila Sol's Silverwind Valley map. You can see the intial highway layout in the white line:

https://steamuserimages-a.akamaihd.net/ugc/924802734825461916/2C56CD27ACF4E76103920FB026641BFD8D5BE608/

I thought maybe since they are trying to reach the other end they figure it's quicker to just U-turn, but this started at the original intersection in the middle of the map and I never saw this behavior when the map had the one way freeways that spanned the map. But seriously it is JUST tourists. I click their RV and it says "tourist - leaving the city". I only have a population of 13,000 so it's a pretty small town, maybe there's no reason for them to really want to stay in town yet? But why even spawn them in that case? I don't have any mods that affect AI so I don't know what to do here.

i didn"t mean the entrance and exit of the highway going one direction, but the entrance and exit the "tourists" are taking, the opposite directions of the supposedly same highway

[chronofanz]

I'm a little disappointed the devs didn't fix this problem. This bug affected me as well.

https://forum.paradoxplaza.com/forum/index.php?threads/cities-skylines-steam-tourists-cannot-despawn-at-two-lane-road-outside-connection.1113430/

The problem stems from us using a 2 lane road to connect to the outside. If you changed to a 4 lane road, I think that would prevent future problems.

I also have a suggested code fix, if anybody is interested in creating or altering their mod to fix the problem.

Essentially, the problem is that these tourists previously tried to travel out of the city along that road, but could not despawn. And they then enter this "infinite loop" where they come back into the city and try again and again to exit through that border point.

[leftbehind]

@chronofanz That's the sort of thing we could certainly look at fixing in TMPE (although it might b better in a small mod). If you want to discuss, create an issue on TMPE issue tracker with basic savegame illustrating the problem (as few mods/assets as possible please): https://github.com/krzychu124/Cities-Skylines-Traffic-Manager-President-Edition/issues/new

[Rena]

Maybe instead of looking at the internals of the traffic algorithm, look at it as realism: that route looks to be the only legal way to turn around on the highway. Unless you're saying you provided a better way and it's not being used?

[chronofanz]

Originally posted by aubergine18:

@chronofanz That's the sort of thing we could certainly look at fixing in TMPE (although it might b better in a small mod). If you want to discuss, create an issue on TMPE issue tracker with basic savegame illustrating the problem (as few mods/assets as possible please): https://github.com/krzychu124/Cities-Skylines-Traffic-Manager-President-Edition/issues/new

Thanks @aubergine18. I opened:

https://github.com/krzychu124/Cities-Skylines-Traffic-Manager-President-Edition/issues/273

Essentially, the suggested fix is to prevent the citizen from adjusting their target position by leaving a vehicle if they are at an outside connection.

[Catratio]

I don't use 81 tiles mod, just 5x5 but I guess the principle is the same. What I don't understand is why I didn't encounter this as badly when it was just the default 3 lane freeways running across the map. I never saw cars exit the main intersection into the city just to turn around the block and leave again like they do here. I'm going to delete this connection since it is right at the edge of the map and see if it improves. Maybe split the highway into separate one way freeways too running off the other side of the map might signal to them that it's fast to just keep going forward?

[chronofanz]

Originally posted by Catratio:

I don't use 81 tiles mod, just 5x5 but I guess the principle is the same. What I don't understand is why I didn't encounter this as badly when it was just the default 3 lane freeways running across the map. I never saw cars exit the main intersection into the city just to turn around the block and leave again like they do here. I'm going to delete this connection since it is right at the edge of the map and see if it improves. Maybe split the highway into separate one way freeways too running off the other side of the map might signal to them that it's fast to just keep going forward?

If you have separate one way freeways going in and out of town, that will also solve the problem.