Intercity traffic

[Piteri]

Hello,
I have recently been playing Sim City 4 lately with the latest version of NAM and traffic simulator z. I have been playing with the traffic route query tool lately and I have encountered an error. I understand the limitations of the route query limiting at 65535 commuters and have calculated my highway to be servicing 230,000 sims in commute. This is not my issue.
My issue is that there is no traffic shown on its neighbouring cities, a problem that I find bothersome. In its neighbouring city the traffic flow should increase from its current 10,000 commuters from another city to 240,000 however the connection with the 230k registers 0 traffic flow. There is 1 cloverleaf interchange connecting the two roads together.

[b22rian]

i am sure Steve ( Z) , will have some comments but i will explain a  few things
if I may..

1) First traffic errors once you cross your main city tile into other cities is very common.
    Maxis short changed us a bit when it comes to neighbor connections always
   functioning as they should.. however, (2)

2) It may be helpful if you can post a couple of pics of how your neighbor
    connections have been constructed. One pic for each city if you please..
   And than we can go from there. There are times however when I am sure
   I have constructed the neighbor connections correctly in my own cities
   and for whatever reason the traffic is counted incorrectly.

Hope this helps some.

thanks, Brian

[Piteri]

I have searched the forum and learned about NAM and path finding, the issue was that I had simply not allotted enough time for new paths to be created (4 month cycle). The traffic is now congesting my neighbouring city. You have answered why the numbers are not the same, I appreciate it.
I have a few more questions related to NAM but I am not entirely sure if I should make a new topic (for other users to search) or continue here.

[b22rian]

I have searched the forum and learned about NAM and path finding, the issue was that I had simply not allotted enough time for new paths to be created (4 month cycle). The traffic is now congesting my neighbouring city. You have answered why the numbers are not the same, I appreciate it.
I have a few more questions related to NAM but I am not entirely sure if I should make a new topic (for other users to search) or continue here.

I am very happy you figured out the issues..
In fact in certain more complex transit set ups, it can take years rather than
game months for the traffic Sim to be fully updated.. Steve and I typically use
5 game years just to be fully sure

[Piteri]

I have run black box tests and observed similar results after I got back to my sim city.
Do you or z/Steve know anything of the capacity effects on congestion (apart from the nominal 30% drop in speed). I am wondering if my game will continue to run if I drop capacity from ultra to a lower level. I like seeing congestion in my cities and especially on my highways ( and I build accordingly to combat it as a challenge ).
Would appreciate a response,
Peter

[z]

You will probably be surprised to find that you can drop your simulator capacity all the way down to Classic and your city will still run.  In fact, you could use the Network Capacity Multiplier in the Traffic Simulator Configuration Tool to make your capacities 10% of Classic, and your city would still run.  You'd just have congestion all over the place.

Why can you reduce capacities arbitrarily low in the NAM simulator without disastrous effects?  It has to do with the 30% minimum speed that's hardwired into the simulator.  No matter how much traffic you have, speed will never drop below 30% of the nominal speed.

If you think about it, this means that all networks really have infinite capacity.  What's labeled as their capacity is simply the volume above which they start to get congested.  Full congestion (the 70% speed reduction) happens at 250% of nominal capacity.

Meanwhile, if you want to know what congestion really does in your city, here's an excerpt from a post I wrote a few years ago.  (Simulator Z is the predecessor to the current NAM traffic simulator.)

Excessive traffic congestion can result in an increase in noise levels that makes residential areas less desirable, an increase in pollution, and a decrease of up to 14 points from neutral in the local Mayor Rating, or much as a 28 decrease from optimal in the local Mayor Rating.  Furthermore, these effects all have side effects themselves.  For example the lower Mayor Rating can be a contributing cause to riots in your city; this effect has actually been observed in Simulator Z Classic, which has the very low network capacities of the original Maxis simulator.  If your congestion is widespread, this can have a significant effect on your global Mayor Rating, which affects which rewards you can get.  To quote the Prima Guide regarding the awards:

In addition... they improve your city in myriad other ways (enhancing desirability, boosting EQ or HQ, further increasing Mayor Rating, to name a few).

Note the last point.  This means that bad traffic can eventually cost you a lot more than 14 to 28 points in your Mayor Rating, ending up having a very major effect on the game, even with no abandonment due to commute time.  And abandonment due to demand may still happen, of course, and if you look at the above quote, you can see how bad traffic can start a cycle than can result in exactly that.  So depending on the level of congestion, any number of bad things can happen to your city.



There's one other important way that congestion can have a major effect on the difficulty of game play, and that's in commute time.  A lack of suitable transportation networks in a city may also cause the same problem, even if no congestion is present.  You may remember from earlier in this thread that in experiments to test the effect of the pathfinding heuristic, we found that in large cities, a higher pathfinding heuristic made the city less attractive to high-wealth Sims.  A short form of putting this causal relationship would be the following:

Pathfinding Heuristic => Desirability

We knew there had to be more intervening steps, but we didn't know what they were at the time.  I have since done some more research, and discovered the details of how this mechanism works.  It's not that much more complicated than the above statement, and can be stated as such:

Pathfinding Heuristic => Commute Time => Desirability

By definition, the higher the pathfinding heuristic, the higher the commute time.  Yet as I have stated many times, the maximum commute time in Simulator Z is effectively unlimited.  However, I'm sure you're all familiar with the short, medium, and long commute times that can be displayed when you query a residence.  And long commute times specifically reduce the desirability of the residences of the Sims who are commuting.  Reduced desirability in can be a big factor in why a building downgrades in wealth status.  So this is how a higher pathfinding heuristic can make a city less attractive to high-wealth Sims.

As for how this applies to congestion, congestion lengthens commute times.  Depending on the level of congestion, this can increase the number of long commute times a little or a lot.  When it increases them significantly, you get reduction in desirability, and you may start to see your high- and mid-wealth Sims leave town, replaced by low-wealth Sims.  On the other hand, a short commute time results in higher residential desirability, essentially helping to attract high-wealth Sims to your city.

So I hope I have shown that there is a lot more to the effects of traffic congestion than meets the eye, and I hope that this information will be useful in selecting a traffic simulator for your city that provides the level of challenge that you want.

[NCGAIO]

Why can you reduce capacities arbitrarily low in the NAM simulator without disastrous effects?  It has to do with the 30% minimum speed that's hardwired into the simulator. No matter how much traffic you have, speed will never drop below 30% of the nominal speed.

If you think about it, this means that all networks really have infinite capacity.  What's labeled as their capacity is simply the volume above which they start to get congested. Full congestion (the 70% speed reduction) happens at 250% of nominal capacity.

  Just to clarify, if the two conditions occur - 30% and 70% - then it would correct the principle that no matter how much traffic there is the rate will never fall below 30% of nominal?


Edit: Sorry .... I realized now that you meant "a reduction for 70% of the nominal value" and not a reduction of 70%.

[Piteri]

I appreciate your in depth response and it's pleasing to hear that there is a robust nature to Sim City (ever rare).