NAM Traffic Simulator Development and Theory

[z]

I am starting this thread to describe a new traffic simulator I have built.  I will be explaining why I built it, what its major features are, implementation details and rationale, and plans for testing and feedback.  I will decide what to do next depending on the feedback I receive.

Before anything else, I would like to thank all of those who have gone before me and helped bring SC4 traffic simulation to its current state.  I would especially like to thank jplumbley and mott, who not only created our current state-of-the-art simulators, but who also have been such a great help to the whole community by taking the time to do so much explaining about how these simulators work.  I would also like to give special thanks to jplumbley, who not only read and answered my almost endless questions in great detail, but who also gave great consideration to all my arguments.

So why did I build this simulator?  For the benefit of those who have managed to avoid my posts until now, I should mention that for many months, I have been building a large simulation of Chicago to scale.  I have tried to make it as realistic as possible, so it includes about 98% of all streets and roads, every highway, every rail line (passenger and elevated) and every park that is in the actual city.  All are exactly to scale, and all are in their actual places.  With a few exceptions, I also avoided adding anything that is not in the actual city.  And, very importantly, I zoned my city to match up as closely as possible with the real one.

Now using the available traffic simulators, this is not a recipe for success.  There are all sorts of good practices about where to put residences, where to put businesses and industry, how far apart zones should be, what a good road system should look like, etc.  But as these practices were designed for SC4, the great City of Chicago knows nothing about them, and so my simulation makes no effort to follow them either.  For the first few tiles, things went reasonably OK.  But as I began building more tiles farther from downtown, and their RCI populations became more and more unbalanced from SC4's perspective, things became more and more difficult.  The Sims needed to commute to downtown, where there were now more than a million vacant jobs.  But they wouldn't.  Instead, I got more and more buildings abandoned due to commute time too long, and things just really started going downhill.

At this time I was using CAM and the CAM traffic simulator.  When Simulators A and B came out, I tried them, but they only made things worse.  These are excellent simulators, but they simply weren't designed for long distance, multi-tile commuting.  The general opinion that I saw was that such a thing wasn't even possible in SC4.  After all, you have the eternal commuter problem, the time warp and all the weirdness it introduces, and then all the ramifications from the fact that different cities in a region are quite separate, and don't really have much communication with each other.  Nevertheless, I figured that by starting with the CAM simulator, which I was using because it worked best for me, and then tweaking it, I could get things to work a fair amount better than they were.

I succeeded in doing this, and actually accomplished a whole lot more than I originally thought was possible.  The first iteration of my simulator is now complete, and I have successfully tested it on all my cities.  It has the following features:

1. More realistic commute time.  I have adjusted the commute time to match real-world experiences.  As long as a region has suitable jobs for its Sims, they should be able to find them.  Multi-tile commuting works much better.  At this point, I can't say how much, as the developed part of my region is still relatively small.

2. More realistic zone placement.  This has been a bugaboo of SC4 from the beginning.  If you just placed zones willy-nilly where you felt like, all over the map, you usually got into trouble fast.  But real cities are like this; in the real world, you can't count on any particular placement of zones.  This simulator gives you much more latitude in where the zones are placed.

3. More realistic car usage.  I've seen figures that 88% of commuting in American cities is done by car.  In Europe, the figure is 78%, but it is fast approaching the American figure.  But you'd never know that looking at your typical Sim City.  The Maxis traffic simulator is heavily biased toward mass transit, and as far as I know, no one has tried changing that bias in a production traffic simulator.  I checked the traffic in my own cities via the Traffic Volume graph.  I always build excellent mass transit systems, but still, I was surprised at what I saw.  Among all my cities, car usage varied from 3% to 7% of total traffic.  Not very realistic at all.  So I increased car usage, and adjusted various other things to make it work seamlessly.  In my cities, this change resulted in increasing car usage by a factor of between 2.5 and 6, depending on the city.  In no city did car traffic reach 25%.  (I had the Commuter Shuttle Service Ordinance turned on for these tests, but as I describe below in the implementation section, it doesn't make a significant difference.)  Car traffic won't approach the real-world figure of 88% for anyone (at least not in this version  ), but traffic is more in balance.  There have been no negative effects that I have been able to see as a result of this change; for example, Sims still walk to work whenever it's reasonable.

4. More realistic routing.  Due to the fact that the Maxis pathfinding algorithms don't pay much attention to route speed, realistic routing has always been a problem with traffic simulators.  In response, jplumbley had the clever idea to use congestion to force better routing in Simulators A and B.  This works very well, but has the unfortunate side effect of, well, congestion.  My simulator gets better routing than older ones (pre-2008) without forcing congestion.  I don't know how it compares to Simulators A and B, as I haven't done extensive testing of them.  I will be interested to find out how it does from people who test these simulators side by side.

5. Greatly reduced abandonment due to commute time problems.  As you might expect, this follows from the first point.  One of my all-time favorite quotes from this game is from someone who said, "These Sims are so stupid, they couldn't find a job if their lives depended on it!"  As I said in a recent post:

In the real world, you just don't see abandonment due to commute time.  Buildings may be abandoned due to lack of desirability or lack of demand, both of which occur in SC4 as well.  But not commute time.  Sure, individuals in a building may decide their commute is too long and move somewhere else, but the whole building?  Doesn't happen.

By adjusting the traffic simulator, I have been able to eliminate most of this problem.  In many of my cities, this problem no longer occurs at all.  In some of my "problem" cities (i.e., those where the layout of Chicago does not come close to matching SC4 guidelines), this type of abandonment has been greatly reduced to a small fraction of what it was before.  This problem can also be addressed in the area that the CAM people are working, and I'm going to be talking to them about this soon.  In the mean time, this problem is mostly gone.

6. Significantly faster execution.  In typical medium to large cities, the game runs more than twice as fast at high speed when this simulator is used, and the difference in speed grows as the population of the city grows.  The reason for this is that I have been able to eliminate some of the exponential properties of the pathfinder which are still present in Simulators A and B.  And since the traffic simulator accounts for only part of the time it takes to run the game, a doubling of total game speed means that the traffic simulator is running about three to four times faster.

7. Various transportation types are now more effective.  One of the side effects of the better routing in this simulator, which is different from Simulators A and B, is that Sims have a lot more flexibility in how they get to work and back.  Basically, all transportation types are more powerful; this has been done without making any significant changes to transportation speeds.  Previously, in many high-density cities it was necessary to create an entire grid of subways beneath the city to get acceptable performance.  The necessity for this type of layout has been greatly reduced, and subway layout can now be done according to more realistic standards.

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So that's a summary of the new features in this traffic simulator.  I have tested it extensively in all my cities, which range from downtown areas where the commercial population outnumbers the residential 3 to 1, on through more mixed areas, and out to more medium-density, residential areas where there is very little commercial or industrial population.  The simulator works fine in all of these situations; there are no known bugs or problems.  There are clearly a whole range of environments that haven't been tested at all, but I have no reason to believe that the simulator will have any problems with them.  I will be explaining the implementation of the simulator in detail in future posts (don't you think this one is long enough?  ), but I wanted to announce it here and make it available for testing on a limited basis.  As this is really an alpha release at this point, I would like to invite interested members of recognized SC4D teams to try out this simulator.  If you are such a person and would like to try it out, send me a PM or an email with your team affiliation, and I'll send you a copy of the simulator.  Obviously, you need to remove your current simulator in order to run this one.  This simulator works fine in establishes cities; you should have no problem just dropping in this simulator and resuming your city.  You may see the traffic volume graph fluctuate for a few months as the simulator adjusts to the different mix of cars and other traffic, but then it will settle down into a stable pattern.  In the mean time, you should notice no ill effects on your city.

For those who would like a Park 'n' Ride version of this simulator, it's easy to create, or I can create one for you.

Right now, there's just one version of this simulator, which corresponds approximately to the Easy version of Simulators A and B.  At this point, I'm not creating Medium and Difficult simulators, though it's an issue I'm willing to consider; I think that for now, the overall game settings of Easy, Medium, and Hard should be sufficient for adjusting the challenge level.

No other changes to this game or changes to your playing style need to be made to use this simulator.  However, there is one main change I would recommend, especially if you're playing large urban cities and/or using CAM:

High capacity mass transit stations.  I have found that most mass transit stations in this game have too little capacity for their environments.  For details, please see my posts in Cogeo's Transportation Lots.  In my cities, I tend to use mostly cogeo's RTMT stations, along with a scattering of RaphaelNinja's five-way stations.  I would recommend doubling the capacity of RaphaelNinja's stations.  I have files with these capacities implemented if testers would simply like me to send them to them.  If you're using other stations, here are my recommendations for minimum capacities.  They are only approximate, of course.

Bus                    22,000
Subway              22,000
Bus + Subway    28,000
Passenger train    10,000 for Maxis-type station
                          5,000 per tile for inline stations
Elevated rail        20,000
Monorail            20,000

For multi-network stations, you should add about an additional 5,000 capacity for each addional network.  For stations on streets, you can divide the first three numbers by two; for stations on avenues, multiply them by two.

So that's it for now.  For those people who try the simulator now, I'm happy to hear about problems, but please hold off on questions about the implementation until I post my explanation, which will be when I get time.  (I hope to do this within the next week or so.)  Until then, those interested and qualified parties who would like to try this out should contact me.  Try it, I think you'll like it!

[z]

There's a very important point I forgot to make in my first post:  This traffic simulator is in no way intended to replace Simulators A and B.  These latter simulators work extremely well in a wide variety of situations, and huge numbers of people are happy with them just as they are.  My simulator is intended simply to be another choice for people working in situations where its parameters are more appropriate for them than Simulators A or B.  What the exact range of those situations are remains to be seen.

[z]

Q: Will this new traffic simulator work with existing NAM projects, such as NWM, RHW, and high speed rail?

A: Yes, it should be fully compatible with all of them.  Road capacities are normalized to fit the requirements of NWM.  Necessary parameters have been set properly to fit the requirements of RHW.  And though I haven't tested high speed rail, monorail has been tested and works fine, so high speed rail should as well.

Q: If I have further questions about compatibility, functionality, or usage, should I ask them now, or should I wait until you describe the implementation in full?

A: Feel free to ask any questions regarding compatibility, functionality, or usage at this point.

[z]

This is the post explaining the traffic simulator implementation that I promised.  I will be going through the traffic simulator exemplar and explaining where the properties of my simulator differ from those of Simulators A and/or B, and why I made the decisions to change them to what they are.  As there are many changes, this is going to be a long post, so I'm going to add to it in stages.  In the interests of coherence, the additions will simply be edits to the original post.  Originally, I thought I might add a post to this thread notifying people when I had made an addition to the implementation description, but due to the lack of response to this thread so far, I think that may be excessive, and so for now I plan only to announce when the entire description is finished.  If people think I should add notification posts at each stage instead, please let me know.

I have based my implementation and the following description on my knowledge of the traffic simulator.  I have both read extensively what others have written in these forums and others, and performed numerous experiments myself.  Nevertheless, I may have gotten some things wrong.  If you see such an instance, please let me know.

Now on to the description...

Customers/Traffic Noise Coefficient - This number controls both the number of customers businesses receive due to traffic, measured as a function of traffic noise (a good thing), as well as the amount of traffic noise experienced by residences (a bad thing).  More customers means increased desirability for a commercial lot, while more noise means reduced desirability for a residential lot.  So the goal here is to balance this number to the point where businesses receive enough customers, but residential areas aren't too noisy.  Maxis set this number at .128, where it remains in Simulator A, while in Simulator B, it was reduced to .096.  Since my simulator increases the amount of cars significantly, and therefore the amount of traffic noise, I have found that a value of .04 works well here.

Network Speeds - Before getting into the actual speeds themselves, I would like to address the question of what units the speeds are in.  Some people have said that they are have no units associated with them, but various factors make it clear that these speeds are in kph.  Fortunately, the current simulators are all assuming speeds of kph, so it's not necessary to debate that issue here.  Instead, I'll just move on directly to the speeds themselves.  I have found that small changes in these speeds typically do not make much difference in the game, so what has been done here should not be weighted too heavily.  I started with the speeds from the CAM simulator and modified them where I felt appropriate.  As for the speeds themselves:

Walking - 15 kph on all networks where walking is allowed.
Driving - Roads: 50, Highways, 150, Streets: 30, Avenues: 50, One-Ways: 75, RHW: 150, Ground highway: 150.
Bus - Roads: 45, Highways, 150, Streets: 25, Avenues: 45, One-Ways: 65, RHW: 150, Ground highway: 150.
Passenger Train - 140.
Freight Truck - Roads: 40, Highways, 130, Streets: 25, Avenues: 45, One-Ways: 60, RHW: 130, Ground highway: 130.
Freight Train - 105.
Subway - 105.
El Train & GLR - 105.
Monorail, HSR, & BTM - 225.

In general, these speeds are fairly close to those in Simulators A and B, which differ slightly between each other.  I made bus speeds lower than car speeds to take into account intermediate bus stops, which are otherwise invisible to Sims.  I left bus speeds for highways the same as for cars because there are no bus stops on highways.  (RHW may be an exception, but I think any bus stops there are far enough apart not to matter.  I also decided to ignore the fact that if you put a bus stop next to a highway, some Sims will walk into the bus stop, climb up onto the highway, and jump onto the next passing bus.)

Many of the CAM simulator speeds are somewhat higher than the speeds in Simulators A and B, and even the corresponding speeds in real life, yet I left them unchanged.  There are two reasons for this.  First, I wanted to compensate at least somewhat for the limitations in the underlying traffic simulator algorithms.  Since these algorithms don't take speed adequately into account when determining a Sim's path, on average the paths will take longer than optimal.  Increasing speeds by a slight amount offsets this a bit.  Second, I discovered that all other things being equal, a network's speed plays a big role in the probability that Sims will use that network for inter-city travel; in fact, it plays even a bigger role than the math would suggest.  (I'll go more into this in the section on Commute Trip Max Time.)  So the slightly higher CAM speeds are quite useful.  I also felt that the proportion of the various network speeds to each other in the CAM simulator was rather realistic.

As for the other changes I made here, I knocked down the CAM avenue driving speed from 80 to 70.  This is still a little high, but it encourages Sims to use the avenues, which adds somewhat to both the realism and the workability of the simulator.  The other change I made along these lines has to do with elevated train speeds.  Once again, this comes down to the limitation of the traffic simulator algorithms that I just mentioned.  One thing people do to get around this limitation is to use a large network of subway lines beneath their cities, which tends to work very well.  But there are inevitably relatively few elevated rail lines above ground, and with all those intersecting subway lines available, the elevated rail lines don't tend to get used much.  By giving them a slight speed advantage, they get more realistic usage.

Travel strategy percent - This is where the changes were made to increase car usage.  The first of the four entries here is "Travel strategy percent WealthNone."  I'm not sure what that is - background traffic, maybe?  If anyone knows for sure, please post.  In any case, I left it alone.

The next three entries actually control normal commuting traffic choices.  They are described in detail on page 250 of the Prima guide.  Each entry has three numbers, which are the percent probability the Sim of that wealth category will use mass transit for his or her commute, the percent probability the Sim will use a car, and the percent probability that the Sim will choose the best route.  The manual says "fastest route," but of course it isn't necessarily the fastest, nor is it necessarily the shortest; it's simply the best route the simulator knows how to calculate.

The manual also implies that the simulator sticks to these percentages strictly, although it does mention that the Commuter Shuttle Service ordinance alters the numbers more in favor of mass transit.  It doesn't say how much, but my experience is that the difference is fairly small, maybe a few percent for each travel type.  But the implication that with this ordinance turned off, the simulator sticks to the specified percentages exactly is completely wrong.  The simulator treats these numbers as purely advisory.  It pays attention to them, but only to the extent it thinks is best.  Specifically, it will follow the recommendation if and only if that method can get the Sim to work within the Commute Trip Max Time.  Otherwise, it will use the other method, and add a penalty specified by by the Trip Starting Cost by Travel Type properties, which are described below.  The Pathfinding Heuristic also indirectly affects these probabilities by affecting how successful different travel strategies are.  It is also described below.

So here are the standard Maxis probabilities, which are present in all the simulators I have seen.  Each triplet of numbers represent percentage preference for mass transit, car, or best route:

R$      80,20,0
R$$    30,0,70
R$$$  10,80,10

And here are my set of numbers:

R$      70,30,0
R$$    20,70,10
R$$$  10,80,10

For one thing, I thought that these were much more realistic numbers, though still far below the typical percentages I mentioned in my first post.  Also, I noticed no deleterious effects on my cities from switching from the first set of numbers to the second one.  Notice that the numbers for R$$$ remain the same; I experimented with changing them to 5,90,5, but this did have a small negative effect in that my R$$$ population immediately dropped slightly.  As my other populations had not suffered from their changes, I thought I should leave the R$$$ numbers alone.

Although car usage did jump in my cities by a factor ranging from 2.5 to 6, what's interesting to note is how far the final traffic volume numbers were from the percentages above.  Using strictly those numbers, you would have expected to see about twice the car usage that I saw.  It is possible to enforce these numbers strictly using the abovementioned Trip Starting Cost by Travel Type properties, but as I discuss in their section below, it's not a good idea.  So for now, these seem like good numbers that produce a reasonable balance of traffic.

Pathfinding Heuristic - This is by far one of the most important numbers in the traffic simulator.  Basically, it's a measure of the accuracy of the pathfinding algorithm, which is what is used to determine a Sim's path to and from work.  The lower this number, the more accurate the algorithm.  Still, the accuracy of pathfinding in the game is limited by the nature of the algorithm used.  The one used in the traffic simulator primarily looks at distance, and tries to find the shortest path.  Speed is only a secondary consideration, although it does figure into the calculations.  So does traffic congestion, which of course has an effect on speed.

Instead of going through all the implications of this, along with the principles of heuristic pathfinding, I would refer the interested reader to mott's excellent dissertation on this topic, which can be found here (mostly in the large post).  In terms of principles of operation, there's really nothing I can add that he hasn't already written.

Now that you are all experts on heuristic pathfinding, how does this apply to the game?  Well, we want the best pathfinding possible, which means the lowest number we can use for this paramater.  In the vanilla versions of the game, this parameter is set to 0.09, which results in very mediocre pathfinding at best.  With this number, Sims often do not find an optimal path from home to work, and as a result, the simulator may decide that commute time is too long and abandon a building, even if there are jobs within commuting range.  As mott pointed out, one big reason that Maxis chose such a relatively high number was that when this game was released in 2003, computers could not be guaranteed to have the processing power to handle lower numbers.  (More accurate pathfinding tends to take more CPU time, as you would expect.)

Once the NAM came out, lower numbers were tried for this parameter.  For example, the traffic simulator packaged with the CAM uses a value of 0.0465, which while still relatively high, is a big improvement over 0.09.  Then we come to the current simulators, A and B, which use values of 0.009 and 0.025, respectively.  (Since mott built Simulator B, and he also showed that a value of 0.003 resulted in essentially perfect pathfinding, I'm somewhat puzzled by why he chose such a relatively large value for his simulator.  Especially when he said, "Stick with the 0.003 heuristic for now, I'd say."  Does anyone know why?  Mott?)  Originally, I chose a value of 0.009 for my simulator, the same as is used in Simulator A.  Moving from CAM's 0.465 to 0.009 had immediate and dramatic results.  In one city, a traffic jam that had been present for literally centuries disappeared overnight.  Why?  What appears to have happened is that the simulator now spent more time finding the best individual route for each Sim, and this tended to spread traffic over a wider area.  In a similar vein, the simulator appeared to become smarter at avoiding congestion, again by spreading out traffic.  While doing so, it would find faster routes, and the speed of the routes became more significant.  Highways started becoming used more.  So traffic patterns as a whole became more realistic.

What about mott's magic number of 0.003?  As mott points out, for reasons which he details, CPU usage does not grow exponentially as this number declines.  In fact, it doesn't necessarily decline even linearly.  So I tried it out.  As expected, pathfinding became even more realistic.  So did commuting patterns as Sims started heading downtown from other tiles, even nonadjacent tiles.  I found one development to be particularly noteworthy.  I had already made the change to increase car usage in all my cities quite a while ago, but in my Downtown city, when I dropped the pathfinding heuristic to 0.003, car usage increased immediately even more, along with increased road congestion.  I found this rather puzzling, so I asked, "Why, O Perfect Pathfinding Algorithm, why is this happening?"  And it responded, "Look at the commute times, dummy."  Ignoring the insult from the algorithm, I looked at the commute times, and sure enough, they had dropped.  So the traffic simulator was now smart enough to figure out that by moving more Sims into cars, even at the expense of creating more traffic congestion, it could get them to work faster than by using my extensive mass transit system.  I was impressed.

As for performance, I found that in some cities, this value resulted in performance no worse than, and perhaps even a little better than, a value of 0.009.  I'm sure that mott would not be surprised.  Unfortunately, in other cities, performance took a big hit, so big, in fact, that the game spent almost all its time running the traffic simulator.  When this happens, Sim time does not move forward, and so this was unacceptable.

I went back to mott's posts and read through them again.  This time I noticed the part where he mentioned that having many steps in the congestion vs. speed curve (see below) could speed up the algorithm greatly.  So I added a number of more steps to my congestion vs. speed curve, without changing the shape of the curve.  Bingo!  I could now run with a pathfinding heuristic of 0.003 in my cities with quite acceptable performance.  Subjectively, it seems no worse anywhere than when I was using 0.009, and in some places it seems better.  So my present simulator uses the value of 0.003, which according to mott, results in the "perfect" version of the pathfinder.

I noticed that one city runs a fair amount slower than the others using a value of 0.003.  Depending on the results of wider testing, it may be wise to create two versions of the simulator (at least from the perspective of pathfinding), with one version using "better" pathfinding with a heuristic of 0.009, and the other using "best" pathfinding with a heuristic of 0.003.  There is certainly ample precedent for this.

Congestion to Accident Probability - I spent quite a bit of time researching this issue at the Google Institute of Traffic Engineering.  The final result I found was:  It depends.  It depends on what country you're in, which region of the country, whether it's rural or urban, what type of neighborhood if it's urban, what the weather is, what kinds of roads you're talking about, etc.  As you might expect, with all of these factors involved, there's a wide variation of plausible numbers.  Both the Maxis numbers and the numbers in Simulators A and B fall within the range of plausible numbers.  For simplicity's sake, I chose to stick with the Maxis numbers.

Network Traffic Capacity - This property is one of the most important in any traffic simulator, and this simulator is no exception.  The proper values for these capacities are dependent on many other properties in the simulator, though, so network capacities for one traffic simulator are not necessarily comparable to those of a different simulator.  This is especially true in the case of this simulator.  The capacities I have chosen here are all based on real-world capacities, yet they are much higher than for most traffic simulators in use.  This does not mean that this is a "super-easy" simulator.  To the contrary, I have verified that all network types can get congested beyond 100% capacity in a realistic city environment.

Essentially, higher capacities are required because this simulator, by being more realistic, produces more traffic.  For example, the Commute Trip Max Time is much larger in this simulator than in most others, leading to trips that are longer on average for most Sims.  Since the Sims are traveling longer times on all networks, this factor alone results in higher network traffic at any given time.  Furthermore, the higher Commute Trip Max Time makes it possible for more Sims to get to more jobs, further increasing traffic.  A third factor, which has been mentioned above, is that the change in the Travel Strategy Percent results in their being 2.5 to 6 times as many car trips as there would be in other simulators.  This number has a multiplicative effect on the previous number.  A fourth factor is that the intersection capacity effect is strengthened in this simulator, further slowing down traffic, and adding to the number of cars and buses on the road at any given time.  Finally, inter-city traffic is much more common, meaning that networks have to handle not only traffic from their cities, but sometimes significant amounts from neighboring cities as well.  All of these factors are designed to make the game more realistic, and they all result in network capacities that are more realistic as well.

With this in mind, here are the network capacities currently in use for all versions of this simulator.  As is customary, all capacities are expressed per tile.

[tabular type=2]
[row] [head]Network[/head] [head]Classic[/head] [head]Low[/head] [head]Medium[/head] [head]High[/head] [head]Ultra[/head] [/row]
[row] [data]Street[/data] [data]100[/data] [data]1500[/data] [data]2400[/data] [data]3600[/data] [data]7200[/data] [/row]
[row] [data]Road[/data] [data]1200[/data] [data]2400[/data] [data]4000[/data] [data]6000[/data] [data]12,000[/data] [/row]
[row] [data]Avenue[/data] [data]1400[/data] [data]2400[/data] [data]4000[/data] [data]6000[/data] [data]12,000[/data] [/row]
[row] [data]One-way Road[/data] [data]1800[/data] [data]3600[/data] [data]6000[/data] [data]9000[/data] [data]18,000[/data] [/row]
[row] [data]Rail[/data] [data]3000[/data] [data]10,000[/data] [data]16,000[/data] [data]30,000[/data] [data]65,200[/data] [/row]
[row] [data]Subway[/data] [data]3000[/data] [data]10,000[/data] [data]16,000[/data] [data]30,000[/data] [data]65,200[/data] [/row]
[row] [data]Elevated Rail[/data] [data]3000[/data] [data]10,000[/data] [data]16,000[/data] [data]30,000[/data] [data]65,200[/data] [/row]
[row] [data]Monorail[/data] [data]3000[/data] [data]10,000[/data] [data]16,000[/data] [data]30,000[/data] [data]65,200[/data] [/row]
[row] [data]RHW[/data] [data]2700[/data] [data]6000[/data] [data]10,000[/data] [data]15,000[/data] [data]30,000[/data] [/row]
[row] [data]Highway[/data] [data]4000[/data] [data]9000[/data] [data]15,000[/data] [data]22,500[/data] [data]45,000[/data] [/row]
[row] [data]Ground Highway[/data] [data]4000[/data] [data]9000[/data] [data]15,000[/data] [data]22,500[/data] [data]45,000[/data] [/row]
[/tabular]

Some of these figures may seem to be high, especially the rails.  But if you look at real-life rail lines they're actually quite reasonable.  For example, the new Second Avenue Subway in New York is designed to carry 600,000 passengers per day.  So if you were trying to simulate a real New York City, you couldn't do it, even with these capacities.  Fortunately, most people aren't building New York City, and the game doesn't require such high capacities.  But the capacities in this simulator do seem to fit in with actual game usage quite well.

[FrankU]

Z,

You have been doing a lot of work! Wow! 

I am curious of what this is leading to.
I am not a traffic simulator expert, know almost nothing of it, so I cannot help you, but I will surely follow the discussion.
Thanks for your elaborate work and explanations.

[b22rian]

Hi Z....

You have put a lot of work and effort into all this.. and it looks like so far from reading your posts your doing
quite well with this.. I just wanted to thank you for providing more enjoyable playing options to this community..
What your doing trying to replicate the city of Chicago I find quite interesting and I hope you will continue
to update us with your progress with that..

also . especially considering what your doing yourself ..i do indeed understand your point about wanting to replicate
more closely real life city traffic conditions and transit modes.. No question your going to find those who would be happy to try out your new traffic simulator.. As you know there are those where realism is quite important to them and than you have others who sI'mply see what there doing as more a "game".. perhaps lost in their own visions of
what they have created or evolving towards.. Different strokes for different folks as they say..

In the region I'm working on now im currently using the Cam like you are using.. and traffic sim B on hard difficulty
currently most of my time has been spent on my largest city which is at about 700 K now.. I look forward to the challenges as i approach a million in population of keeping this at hard difficulty level for as long as I'm able to..
So far Ive been quite pleased actually with all the  mass transit types  and also the highway system i have created for car use.. There seems to be a very good balance in the way i have designed this city in terms of Mt versus car usage.. but obviously Ive had to design it that way once I was used to the traffic sim itself and how i saw the city evolving over time as it grew larger.. But so far Ive done a good job in terms of the fact i have seen very little abandonment due to commutes times or any traffic related problems.. Obviously these challenges will become more difficult as the city grows larger, but than thats a big reason i enjoy playing this game too.. In short i suppose I'm a player who is currently satisfied with what I'm working on ...

But having said that, you deserve a lot of credit for not only creating more enjoyable playing options for the people of this community.. but also in that your taking the time to explain what your doing.. providing important information about many aspects of this and your also doing it in a very thoughtful and articulate manner..
I just want you to know i appreciate what your doing with all this..
And when I'm ready to start a new city and region I would be more than happy to give your new traffic sim a go..
and provide you with as much feedback as my knowledge with all this will allow me to give you..

Thanks for all your time and efforts you have put into this so far..

Brian

[CasperVg]

That looks like a very interesting traffic simulator. I would like to request, however, to create a (very) difficult version. I, for one, have always loved to use the Hard simulators, because I like to fix the issues that may arise from low capacities 

[z]

That looks like a very interesting traffic simulator. I would like to request, however, to create a (very) difficult version. I, for one, have always loved to use the Hard simulators, because I like to fix the issues that may arise from low capacities 

I have been thinking more about other versions, and I have some ideas.  Not by lowering capacities, but by making it even more realistic.  Instead of 20% to 25% cars, 80% cars!  (With no added road capacity; it's already realistic in this simulator.)  Multiply the cost of subway tiles by 50.  Make intersections really act like intersections (they don't now) and slow down road traffic even more!  All of these are just extra realism (and they are very realistic), but they would give you a very difficult version, to be sure.  A version of intermediate difficulty would then also be possible.

[FrankU]

Make intersections really act like intersections (they don't now) and slow down road traffic even more! 

Do you mean by this that intersections do not slow down commute time? Meaning that it is not important wether I put two or twohundred intersections between my house and my office? Well, that is really unrealistic. It would be nice if you could change that. There even could be a difference in capacity and speed between intersections with or without streetlights, roundabouts, threeway, fourway etc....

[CasperVg]

I have been thinking more about other versions, and I have some ideas.  Not by lowering capacities, but by making it even more realistic.  Instead of 20% to 25% cars, 80% cars!  (With no added road capacity; it's already realistic in this simulator.)  Multiply the cost of subway tiles by 50.  Make intersections really act like intersections (they don't now) and slow down road traffic even more!  All of these are just extra realism (and they are very realistic), but they would give you a very difficult version, to be sure.  A version of intermediate difficulty would then also be possible.

That sounds like heaven! 

[z]

Do you mean by this that intersections do not slow down commute time? Meaning that it is not important wether I put two or twohundred intersections between my house and my office? Well, that is really unrealistic. It would be nice if you could change that. There even could be a difference in capacity and speed between intersections with or without streetlights, roundabouts, threeway, fourway etc....

For the most part, they don't.  The traffic simulators handle intersections by temporarily reducing network capacity.  By default, it's reduced by 30% in the intersection square, 20% one square away, and 10% two squares away.  Simulators A and B are even more lenient than this.

Note that the speed is not reduced (at least not directly), only the capacity.  So if a road intersection is at 70% or less of capacity, the Sims don't even take their foot off the accelerator as they zoom through.  This is regardless of how many pretty stoplights you have at the intersection and what the automata look like they're doing.  And even if the network is running at a higher capacity, the Sims just slow down a bit; only in highly congested traffic do they slow down significantly, and even then, typically just for a square or two.  They never stop, much less wait for an entire stoplight cycle.  If I were a policeman in Sim City, I could make a simulated fortune writing tickets to Sims who run red lights, because they all do, every time.  At busy intersections, they just do it a bit more slowly than at others.

Now it's not possible to actually make the Sims stop at intersections.  But it is possible to drop the intersection capacity numbers down far enough to have the same effect.

Meanwhile, the easiest way to see the effect of intersections is to look at the Traffic Congestion View.  For any intersections that are pure green, your Sims are driving through them as if they're not there.

[FrankU]

Aha!
Thanks.

So now I also know why SC shows us traffic accidents instead of waiting rows at congested streets. They don't stop, so they clash into each other. 
But that is quite an unrealistic simulation then. Especially because the sims won't search for another route as to avoid the congested sqares.... They just jump on each other's necks on the intersection and crash their respective cars.... Not too smart..

One disappointment for you though: your sims won't stop, so they aren't able to receive the tickets and as there is no postal system in SC4 (have you ever seen a post office?) you cannot send the tickets by post. 

[Rayden]

Aha!
Thanks.

So now I also know why SC shows us traffic accidents instead of waiting rows at congested streets. They don't stop, so they clash into each other. 
But that is quite an unrealistic simulation then. Especially because the sims won't search for another route as to avoid the congested sqares.... They just jump on each other's necks on the intersection and crash their respective cars.... Not too smart..

One disappointment for you though: your sims won't stop, so they aren't able to receive the tickets and as there is no postal system in SC4 (have you ever seen a post office?) you cannot send the tickets by post. 

I'm sure Equinox's post office would manage that - http://www.simtropolis.com/stex/index.cfm?id=15266http://www.simtropolis.com/stex/index.cfm?id=15266

Good work z, I'm following this with great interest.

[z]

Aha!
Thanks.

So now I also know why SC shows us traffic accidents instead of waiting rows at congested streets. They don't stop, so they clash into each other. 
But that is quite an unrealistic simulation then. Especially because the sims won't search for another route as to avoid the congested sqares.... They just jump on each other's necks on the intersection and crash their respective cars.... Not too smart..

Actually, this is not the way it works.  Accidents are purely a function of congestion.  There's a table in the traffic simulator that links the level of congestion to the probability of an accident.  So accidents aren't specifically tied to intersections, other than by the level of congestion at the intersection.

Also, when any route gets congested enough (including intersections), the simulator does start looking for alternate routes.  Intentional use of congestion for this purpose is one of the main features of Simulators A and B.

One disappointment for you though: your sims won't stop, so they aren't able to receive the tickets and as there is no postal system in SC4 (have you ever seen a post office?) you cannot send the tickets by post.   

I'm sure Equinox's post office would manage that

It sure does, and it's sitting right in my downtown Chicago, where it belongs.  It's a really cool building - have you ever driven through a post office on an expressway?  I was fortunate emough to have done this may times when I still lived in Chicago.

[Rayden]

It sure does, and it's sitting right in my downtown Chicago, where it belongs.  It's a really cool building - have you ever driven through a post office on an expressway?  I was fortunate emough to have done this may times when I still lived in Chicago.

That's why I mentioned that one, coz it's in Chicago, and you are doing a Chicago "replica", but there is also around, some other post offices, even a postal delivery service lot, somewhere on the LEX.

[b22rian]

i think using Mott's traffic sim on hard difficulty is somewhat challenging..

Eventually if you keep increasing the population higher and higher you find the challenge your looking for

but i suppose it takes time.. the largest city i have now is a Little over 700 K and I'm starting to get a few network

lines congested now..

[b22rian]

Actually, this is not the way it works.  Accidents are purely a function of congestion.  There's a table in the traffic simulator that links the level of congestion to the probability of an accident.  So accidents aren't specifically tied to intersections, other than by the level of congestion at the intersection.

Yup,  a lot of time hearing those accidents happening also tips me off to congestion on my roads and stuff..

Brian

[redraider147]

ok so lets bring some of my test results to the public....

1. one interesting side effect that i've been able to reproduce over and over again is that my game and cities load twice as fast (if not faster) than before when i was using the NAM traffic simulators...curious...it was the only thing changed.

2. while commute time dropped only slightly over NAM simulator AP, traffic volume decreased, congestion decreased, and population increased. how if all my transportation volume categories decreased is my population rising?

3. my population is increasing, but the amount of abandoned buildings is increasing (all due to commute time)...weird...and commute times are decreasing from before...

4. one curious thing i noticed is that my sims take the freeway to work, but not home...ramps are exactly the same on both sides as i use the feeder road system. they all want to take avenues home from work...

5. is there a park and ride aspect that i might be missing? that seems like it should be my problem...it looks like what happened when i installed the AP simulator and hadn't placed parking garages and lots...


More results to come...

[The_Wind]

hmmm this sounds very intresting, i hope i can see it realesed.

[b22rian]

ok so lets bring some of my test results to the public....


2. while commute time dropped only slightly over NAM simulator AP, traffic volume decreased, congestion decreased, and population increased. how if all my transportation volume categories decreased is my population rising?

Hi red raider thanks for posting some comparisons of the 2 traffic simulators..
but which nam sim is AP ?
Is it one of the new traffic sims from mott and j plumbley A and B with the 3 different levels of difficulty or another
older nam one perhaps ?

Thanks Brian