Commuters leave brains at city limits

[Birdin 10]

(Also posted at https://www.simtropolis.com/forum/messageview.cfm?catid=22&threadid=91390&enterthread=y  ; sorry for double-post, but I want to be sure the experts will see this...)

I've recently started a brand-new region, and currently have six cities basically strung out in a line.  The total population of the region right now is about 150K.  On one end is Maple Pont, then Sandville, then Carson Pass.  Sandville is supposed to be a big job city (mostly industrial: I+C total is nearly twice the R total) and Maple Pont is mostly residential and commercial, with emphasis on education. So there are about 7,500 commuters travelling across the border from Maple Pont to Sandville, mostly by car, but some by bus.  Besides the clogged neighbor connections, all is well in Maple Pont.

In Sandville, however, it's utter lunacy.  Despite plentiful bus stops in the industrial areas, the bus commuters just roll right through to Carson Pass.  As for the car commuters, only about 10% actually stop at jobs in Sandville.  Jobs in Sandville are more than plentiful.  Most of the industrial buildings query with 60 to 100 jobs occupied, but the route query reveals only one or two cars actually being routed there.  (Is this an "occupant leak" issue of some kind?) With 5,000 or so cars just dumped into the next city (which really doesn't have a lot of jobs at all -- not that they'd stop there anyway) you can see where this can become a major traffic problem for a region.

This problem has been present for quite some time for me.  Nearly all commuter traffic which enters a city just drives directly to the very nearest connection to another neighbor city.  If there are jobs closer than that, there's a chance that a few will actually stop there, but this doesn't account for much, as can be seen in Sandville.  Most of the time, this leads to unrealistic traffic flows across the corners of cities, often curling back towards their origin after crossing two or three city borders.

I'm currently using the NAM Beta version 09.04B.04 with "Better Pathfinding" and "10x Commute" along with the various turning lanes and roundabouts, diagonal streets, the custom highway menu option, and radical automata.  I'm using a few other mods which don't relate to transportation, except the roadtop MT, and marginally, the bridge height mod.  My EXE version is 1.1.638.0. 

Could someone with knowledge of how pathfinding works explain how the game decides where a commuter entering a city attempts to go?  Is there any data about the commuters regarding their wealth level, or what type of job they are seeking?  Most importantly, how can I get commuters entering Sandville to actually stop and work *in* Sandville besides cutting off access to all other neighbors?

[jplumbley 5]

Hello Birdin,

Your interest in this subject does not go without vain.  Many of us have wondered why the sims do this.

There have been tests created on this before by some of the most experienced modders.  First off, Sims are stupid.  There is a very good reason for this, but I will get to that.

Ok, the basics of pathfinding from how I understand it (anyone correct me where I am wrong).

1.  There is a "start" and a "destination"

          - The "start" is where the sims live, stating the obvious.

          - The "destination" is where the sims are considered, "employeed".

2.  How do Sims become "employeed"?

          - Sims are "employeed" when they reach a job or a city border.

          - Sims will find a job within the city they are in for the most part, if they can.  If not they will probably goto the closest border with a job in the neighboring city.

          - In region play, the game keeps track of how many jobs are in the neighboring city.  If there are no jobs in the neighboring city no Sims will travel to it.  This means that if you have jobs 2 city tiles away, the Sims will not under any circumstances travel to it through a jobless city.

          - Now, when the Sim finds a city border with a job, it takes one of the "available" jobs and is considered "employeed".  The game does not care if the Sim reaches a specific destination because it is just filling available jobs which are probably in some sort of database stating I have x number of jobs in this tile, without stating where this job is.

3.  What happens when my Sims are in the neighboring city?

          - Sims will do absolutely nothing when they cross borders unless you push play in the neighboring tile.

          - Now, since MAXIS was attempting to get the Sims to actually appear as if they were finding jobs in the neighboring city, the original city keeps track of how many commuters there are.  These commuters are essentially considered the same as if they were at home, so the pathfinding engine will again look for a job for these Sims.  Sometimes this again means going to another border, including the one they just came from, meaning they can go around in circles for eternity never actually reaching a job.

I hope this has explained it better for you.

As for you specific questions:

How can you stop your Sims from commuting to through a city and force them to work in that city?

     The only physical way for you to do this without removing city connections is by removing any jobs in all neighboring city tiles connected to the "job" city tile.

Is there any data on the job wealths in a city and what wealth job the Sims are seeking?

     Yes, the Sim do look for a job with wealth according to their wealth and they will goto the city border with the type of job they are seeking.  When they reach the neighboring city all that is known is what type of job they are seeking and the pathfinding engine will again look for that type of job.  The Sim can choose to goto another city border if he desires.  You must remember, once the Sim crosses a city border and you go into the neighboring city it isnt the same Sim anymore, it is essentially a completely new Sim looking for a job as if he was coming from home.

I myself have had experience with this.  I had a 3 city setup, one large tile beside 2 medium tiles.  The large tile shared borders with both medium tiles and the 2 medium tiles shared a border.  I had jobs in all 3 cities, residents in all 3 cites.  Also, a major ring Highway ran through all 3 cities.  The ring highway actually had neighbor connections that were much faster to get to that the jobs themselves.  So what would happen was, I had thousands of Sims driving in circles around this ring highway and never reaching a job.  I tried many things to stop this from happening, but the only possible way for them to stop was to destroy the system and build it in a different way.

Good luck... but I am afraid to say that this is a limitation of the game's pathfinding engine that cannot be overcome.

[Birdin 10]

Well, Carson Pass *does* have jobs, but not many. (I rarely create cities that purely stick to one zone type...) Each city along the line has a few jobs, and there are a lot of jobs at the other end -- but a lot of residents occupying those jobs. If the game is in fact keeping track of what type of job the commuters are seeking, I wouldn't expect this to happen. Maple Pont (the "origin" city of the problematic commuters) has a lot of the high-end commercial jobs. Sandville has a variety of Industrial jobs. So I'd imagine, if a sim from Maple Pont has to go to Sandville for work, they're probably looking for industrial jobs. (It would appear that it's mostly low-wealth sims heading for Sandville by casual observation...) I suppose it's possible that there just aren't enough of the "correct" jobs in Maple Pont. I've been trying to correct this, by re-zoning low-density, low-wealth residential areas to commercal zones. While the number of commercial jobs has increased (mostly Co) and the overall residential population has decreased slightly, the number of commuters "exported" to Sandville has increased! On the other hand, R$$ has been increasing compared to R$, so I guess it's rather likely that growth in the proper C sectors hasn't been fast enough. Plus, it would seem that the concept of stage limits (which I have come to better understand very recently) is preventing commercial areas from developing as dense as I would hope in Maple Pont...

Well, thanks. At least now I think I know a little more about what to avoid.

[Birdin 10]

Update: I kept working in Maple Pont, adding commercial jobs. Then I noticed that all of the commercial lots that were previously residential were *still* generating trips to Sandville. The only way to eliminate these trips was to de-zone the lots and re-zone them again, which had to be done gradually because typically that meant temporarily eliminating jobs of the very kind that I was trying to create. Anyway, after quite a bit of work, I managed to get the number of Maple Pont to Sandville commuters down to about 1,600, all of which happily routed to industrial and commercial jobs on the near side of Sandville.

[Crissa 1]

What's the moral of the story here?  Don't make it easier to go from one region edge to another than to the city itself?

[jplumbley 5]

The moral of the story is do what you want.  It is not possible to make beautiful cities that have jobs in every city tile and prevent sims from travelling through to another city when better jobs are closer to home.  Unless you want to break your city up into sectors where only specific city tiles are where jobs can be.  In my opinion sectored cities are not very good looking, but I am sure someone will come out and show a beautiful suburb and then a beautiful CBD or a beautiful industrial port.  But they wont show you the city lines or show a city border where both sides have been melded together in photoshop showing how much of a continuous flow their cites can have between city tiles.  But thats just my opinion.

Moral = Play the game how you see fit.  The sims will do what they want with the limited simulator they have.

[spa 968]

Two thing that I have found is useful.

1. Don't develop heavily slanted cities. I tend to have people and jobs intermixed throughout.

2. I only put connections to neighbouring cities in the very middle of each tile. That way commuters entering one city have to actually drive through the city to reach the nearest neighbour connection. It seems to increase the liklehood of them actually going to work. If they enter a tile and a neighbour connection is near I can guarantee you they'll head for it like lemmings running off a cliff.