Station Congestion and Pathfinding.

[BlakeMW 84]

I've been experimenting with station congestion, and I'm sure many people already know this or atleast suspected it! But I couldn't find this exact same testing in these forums so I'm posting my findings.

I've already noticed that Sims will take shortcuts through stations, in fact they treat station exactly the same as road/track, or even prefer station to road/track. And by Sims I mean Pathfinder, the terms are quite interchangable.

What I have here (offscreen ) is a large block of housing, the only way out for Sims is by bus via a single street. Busses don't suffer from congestion so unlimited busses can travel down street with no problem. Anyway this block of housing can provide atleast 10K willing commuters. In the outside region is plenty of jobs for these 10K commuters, and the connection is via a Monorail track. (Like buses, Monorail TRACK has unlimited capacity - emphasis on TRACK! the stations are limited).

Experiments readily show that stations cap at 500% capacity, this means no more sims can pass through the station (no distinction is made between sims boarding at the station and those passing through - this is a huge issue). However the time to pass through the station is constant and independent of congestion, effectively a station either allows a sim through (at < 500%), or blocks them (at > 500%). Sims will take a shortcut through any station with less than 500% capacity - this will be demonstrated in a later screenshot.

Bus stations have a max capacity of 5000, Monorail stations have a max capacity of 10000. The tracks for both have limitless capacity, making them handy for testing.

Here are two screenshots demonstrating why sims taking a shortcut through congested stations is BAADDDD (and as usual, bad is another word for no-job zots).

In this first screenshot in order to get to the second bus stop, the sims take a shortcut through the first bus stop. However this maxes out the capacity on the first bus stop and hence no sims can use it to transfer to the monorail station.

Only 5K sims make it down the monorail tracks.

Now I move the first bus stop so it can no longer be used as a shortcut, now both bus stops are being used to transfer to the monorail station.

The result is 10K sims make it down the monorail track.

Knowing the background behind this little segment of network, I now show the concept of a congested station still being considered a valid shortcut.

As you can see, 5K sims (the limit) choose to take a shortcut through the bus stop on the corner, the other 5K go via the street. Now if a partially congested station took longer to get through than an uncongested station you would expect only 1K sims would path through the bus stop (at this point the station should become congested and take longer to get through than staying on the damn street), the other 9K should find it quicker to take the street. But they don't. Commute time tests show this isn't Sim Stupidity, they actually don't take longer to get through congested stations - altough they are being quite selfish by not allowing other sims to use stations for their intended purpose!

In fact I would go so far to say that station congestion doesn't really exist. The station is either full (no more sims can pass through) or non-full - atleast as far as the path finder is concerned. I think of stations as opaque to further traffic or transparent to traffic. In terms of station capacity, 500% means 100%.

What these results mean in practise is that in order to make an effective high capacity monorail network (or any network for that matter) you MUST NOT place stations on the main line, they must be placed on side tracks and in ways that they cannot possibly be used as a shortcut. This allows the entire capacity of the station to be used by sims who are transferring rather than just passing through. It is also important to watch for sims using bus stops as shortcuts and to move the bus stops or roads if nessecary.

PS: I tested using NAM, no NAM and NAM 5xCapacity, rebuilding stations in between trials. No differences.

[Nik-nik 3]

Wow,

Impressive Grater!

I will think about these considerations when placing bus stops and stations as well.

Thanks

[BlakeMW 84]

Thanks!

Ofcourse I too must redesign much of my networks in light of these tests.

I'd be lying if I said I wasn't overjoyed at the prospect of designing all new station layouts. Just to keep it interesting the most obvious design - laying a parallel track for the station, doesn't work - the pathfinder splits the traffic approximately evenly down each track! Thus atleast one tile must seperate the main track and the station track in order to make the station path 'longer' and prevent it being used as a thoroughfare. Alternately the station can be a deadend and attach to a junction of some description allowing traffic from each direction to use the station.

The most compact designs I've come up with that allow street access on both sides...

Attaching stations to roundabouts seems to be particullary ideal as up to 4 stations can be attached to the roundabout and the least space is wasted - assuming you actually need the roundabout.

[Nik-nik 3]

OK Grater,

I agree with the above. I find it usefull to see that it is better to place a station not on the main line. This will come in handy when placing my stations (Train and monorail) Have you checked how this works with subways? I would assume the same?

[BlakeMW 84]

Subways appear to be immune. I speculate this is because sims board and leave the subway track at the same point - there is no shortcut and thus the straight through traffic actually goes straight through.

[cogeo 960]

Date: 8/2/2005 7:09:28 AM Author:Grater

What these results mean in practise is that in order to make an effective high capacity monorail network (or any network for that matter) you MUST NOT place stations on the main line, they must be placed on side tracks and in ways that they cannot possibly be used as a shortcut. This allows the entire capacity of the station to be used by sims who are transferring rather than just passing through. It is also important to watch for sims using bus stops as shortcuts and to move the bus stops or roads if nessecary. PS: I tested using NAM, no NAM and NAM 5xCapacity, rebuilding stations in between trials. No differences.

quote>

 

I'm sure about the monirails, I have experimented a lot with subways and I can tell you for sure that:

- the through traffic is not added to the station's usage, and I don't think your example points this out either

- if a station is terminal, the tunnel (track) must not protrude off the sation (to the opposite side), otherwise it's usage statistics are mangled (the number of commuters entering/exiting the station does not correspond to the usage)! Weird, but I have tested this a lot. If the track is laid correctly both terminal and thriugh stations have the correct statistics.

 

Also, sims may use busstops not as shortcut, as you said, but to switch buses! Your sims may exit the bus and embark another one if it's more frequently scheduled! ThIs CAN happen!!!

[BlakeMW 84]

That is pure nonsense and based on Reality thinking. In Simcity 4 every single sim gets their own personal bus that takes them exactly where they want to go and stations come equipped with magical short-range teleporters. Sure you can IMAGINE they are getting on a more regulary scheduled bus but that's not how it works in SIMREALITY!

Pure. Nonsense. I. Say.

(Sorry. But while imagination has it's place (and I often employ it) this is the game experiments forum, and for hard testing and facts).

[BlakeMW 84]

Exhibit A:

A commuter city where all commuters are funneled onto one little monorail track in the bottom-right corner (it is the only connection).

Exhibit B:

Said track is bottlenecked by adding a monorail station. Note rampant NJZ's as flow is restricted to 10K commuters.

You may assume that no deception took place, such as reducing the number of jobs available in the outside region or altering track speeds. You may also assume adequate time was given to allow the city to settle in to the new track configuration (altough not so long that the buildings actually abandon). This can easily be tested by anybody.

Note: This is a horrible slum city I built, that's why it looks horrible and slumy. They get subjected to awful experiments.

[dzi 0]

Sorry for asking (it shows that I didn't understand something) but how do your sims get to the monorail track without the monorail station? Via bus stops?

[SC4BOY 21]

Date: 9/1/2005 3:23:46 AM Author: dzi Sorry for asking (it shows that I didn't understand something) but how do your sims get to the monorail track without the monorail station? Via bus stops?

A quick glance shows that there were 2 mono stations before and he added a THIRD station in series on the outgoing track. The 3rd is the blocking station.

 

Grater.. nice job! this shd help a lot of ppl understand more how to puzzle through why the natural solutions for RL dont work for SimRL.. As they say in River City, You've got to know the territory! hehe

[dzi 0]

OK, I see, didn't noticed the stations on the picture, thanks.

And the test is very intresting indeed!

 

BTW, it just got on my mind. Isn't it the same for all the on-road bus stops? Meaning doesn't they block road capacity?

[Superchan 23]

this is funny, i have a suggestion, build more stations and mass transit options to relive conjestion.

[BlakeMW 84]

I need this smiley with an angry face and a single finger pointing up instead of a thumb .

[TheCrybKeeper 301]

I too, wish for such a frowny face, Grater. Hehee.

I know when I am through saying this, you are gonna want to use one too.

 

I never get congestion or traffic issues, or job issues or any issues at all,..... why?  like you said; Sim reality is not Real life. I Grid the city out, based on a numerical formula. I supply only one public transportation venue, like busing and I get zero traffic problems, all green lines in the traffic density window. This has worked for me, up to 263,000 population. It's all in the numbers and always has been with simulations.

 

When attempting to make real world cities, you must deliniate from the fixed numbers. This should cause a large variety of problems. I see this trend occurring, for 100's of Sitizens posting, here at ST.

 

again here are the numbers. what object each number goes to, is the challenge:

 

2x3x6x12x24

 

I already know which numbers apply to each obj. for 90% of the game.

 

Grid it baby! or find a band-aid that works.

[Tropod 144]

EDIT: nvm. I've misread what was posted.

[Colijn 0]

Has the impact of the 'Transit Switch Entry Cost' already been tested? Perhaps it can solve the shortcut-problem.

[BlakeMW 84]

What's that? Search gives nothing particullary useful.

The cost would need to be a time-cost to effect the routefinder, $-costs like Toll Booths don't always work correctely (I think toll booths have both a $-cost and time-cost, but they are seperate, atleast it seems that way).

I'll experiment altough I don't know much about modding.

[Lord Kronos 0]

Grater, this was great! I'd always had a gut feling that stations could affect traffic that way, but I never got around to testing it for myself. Now that we know for certain that stations affect capacity on tracks, I'll definately be designing my networks accordingly.

It will just play havoc with UDI missions involving trains and monorails, as you can't continue through stations onto another station if they are all terminus'

Lord Kronos

[BlakeMW 84]

Awesome! It IS a time cost and it DOES work!

Experimenting with bus stops, a value of 0.025 prevents taking shortcuts in favor of roads, a value of 0.037 for streets.

At the moment I'm testing with a copied bus stop lot, how exactly does one best modify the stations in the game?

Damn these forums are flaky today...

Tested monorail stations. It doesn't seem to allow sims to pass through the station, but it does allow placing the station on a parallel track. 0.01 seems to be enough to stop trains taking longcuts through stations...

I'm not sure what effect track congestion will have on this.

edit:

Longcut and Shortcut

A longcut is taking the long way to take a shortcut through a station. Even a small transit switch cost prevents this. However it seems that Sims can choose to use the rail under a station and thus wont take the long way around a station even if the station has a high switch cost. For some reason they still count as using the station.

[Compromise 1]

Very intresting finds here.

[BlakeMW 84]

After some play testing I've found that for bus stations a switch cost of 0.05 tends to work for uncongested networks, 0.1 gives a fair bit more robustness when intersections start jamming at, and also a value of 0.1 doesn't seem to noticeably reduce bus usage.

And it works great!

I'll have to figure out good values for rail stations too, since it's annoying how the sims keep jumping off the tracks onto every station.

[TheCrybKeeper 301]

Grater: I have one last thing to say; you know your details!

That is how you guessed my Bus usage at 30%, simply by viewing game pics! Okay I have too much to say most of the time, so why be different now...

 

Sometimes I get too cocky for my own good Grater. Sorry about that.

 

What about buses, mixed with subway? Are you saying all tracked Transport acts in this manner or just monorail tracks?

 

[spa 970]

Thanks for the info Grater. It took me a few reads to figure out what exactly everyone was talking about but boy am I glad I did. I went and ran my own test and I found exactly the same results that you did. Also, you're right about the most natural separation of track being ineffective. It just cuts the problem in half rather than solving it. You do have to go one full tile out to see any change. I still had 48 stupid sims cutting into the station even with the extra square of separation, but the other 450 were using the straight route. This is good to know as my current region is quite big and I have used monorail as the main non-bus mass transit option. In some of my denser cities, I'll have to take a look to see if my monorail use is being cut arbitrarily limited by station congestion. I don't think it should be too bad for me though. I have been using Brenda's Modern Monorail stations and their increased capacity should make it so that congestion problem is largely avoided in all, but the most used sections. Still I have some re-engineering to do.

-Sam

[BlakeMW 84]

I've now created a
thread for modding solutions.

There is a download partway down with fixes for bus stop monorail station and elrail station.

[spa 970]

Thanks a bunch! I took a look at one of my denser cities this afternoon and had to conclude that redoing the monorail system would be too radical an undertaking. This hopefully solves most of the problem though. Hopefully I'll just have to relocate a few stations and now, only one tile off instead of two. Keep up the good work and experimenting.

 

Actually, as I think about it, if this works your file should really be an option included with the NAM.

 

-Sam

[mrbarham 4]

this is some really great info, I have been laying my train station on side rails for a while but I hadn't ever made the connection in my mind that if the trains work this way then it was likely that the monorails did too for congestion.

[pnorrell 4]

Uh... What about the often-mentioned advantage of the monorail network, that it is not affected by congestion?

Isn't this discussion actually irrelevant for the monorail network?

Wish we had a "mythbusters" thread around here...

[SC4BOY 21]

I find that making a "bypass" USUALLY works..

Edited cause I forgot the editor "takes out spaces and uses proportional font.

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HOwever this isn't ALWAYS true.. but a bit of watching the staion (just click the input track and output track to the station) IF you see arrows leaving the station that come FROM the INPUT track, AND r "jumping via pedestrian" to get right back on the "OUTPUT" track .. sometimes you don't care .. low volume, etc.. but as traffic gets high, it will almost always matter... A case where the simple siding track DOESN"T work seems to relate to geometry.. the MAIN track graphically is"nearer" to the primary traffic path OR the main is LOOPING near the siding and the "pathfind" gets confused... This is much harder to explain than to just "see" ..for example you have a loop and the station is on the INSIDE of the loop so the path is "short" to the algorithm..If you switch the station to a siding on the opposite of the main it almost always solves this problem

I do have a NEW question (as can be seen I was a participant in the early thread days) is that I THINK that the "stops on the road" such as is done for the NAM is no different than doing this

RRRRRRXRRRRR is = to RRRRRRRSRRRRRR where R is road (street, avenue, etc) and S is a standard BUS STOP (for example) while X is a "ON THE ROAD" stop as done by the NAM.. all busses "short circuit" the stop and NONE bypass it. Hope I've made this clear.. maybe not..

Perhaps others have observations on this. I also have a city now where an avenue "on the road" busstop seems to cause traffic to GO AROUND IT via a road.. odd I think..and NO traffic goes THRU the busstop.. 

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All the traffic goes via the R route and NOT thru the X busstop and the AAAA path which should be shorter.. There is NO traffic on the busstop.. I actaully thought I did't place it right at first and redrew the Avenue thru it... didn't change anything..

Oh pnorrell the track never gets congested, but the STATION gets saturated and then becomes the CHOKE POINT .. NOT the track.. but all sims use the station as was pointed out by Grater.. By using a BYPASS track and puttin the station on the bypass will normally avoid the problem. 

[SC4BOY 21]

Originally posted by: Grater Subways appear to be immune. I speculate this is because sims board and leave the subway track at the same point - there is no shortcut and thus the straight through traffic actually goes straight through.quote>

 

Grater, I am not sure this is true IF you use the NAM modified ONSTREET (road, etc) stops. This is only based on casual observatons in-game, not on quantified data. Do you think they work the same or not? 

Also when a subway gets "congested" .. ie "RED" in traffic screen, does it have an impact on transport by limiting in any way or it just to annoy us?